From c37a1fe2a273207ed0c3802a3728208d26a8ab0d Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 12:30:22 -0500
Subject: [PATCH 01/17] Preliminary gregorian grammer, parser, and tests

---
 pyproject.toml                                |  6 +++
 scripts/generate_gregorian_grammar.py         | 26 ++++++++++
 .../calendars/gregorian/__init__.py           |  3 ++
 .../{gregorian.py => gregorian/converter.py}  |  0
 .../converters/calendars/gregorian/parser.py  | 10 ++++
 .../calendars/gregorian/transformer.py        | 37 +++++++++++++
 src/undate/converters/grammars/gregorian.lark | 30 +++++++++++
 .../grammars/gregorian_multilang.lark         |  4 ++
 .../test_gregorian_converter.py}              |  0
 .../test_gregorian/test_gregorian_parser.py   | 52 +++++++++++++++++++
 10 files changed, 168 insertions(+)
 create mode 100644 scripts/generate_gregorian_grammar.py
 create mode 100644 src/undate/converters/calendars/gregorian/__init__.py
 rename src/undate/converters/calendars/{gregorian.py => gregorian/converter.py} (100%)
 create mode 100644 src/undate/converters/calendars/gregorian/parser.py
 create mode 100644 src/undate/converters/calendars/gregorian/transformer.py
 create mode 100644 src/undate/converters/grammars/gregorian.lark
 create mode 100644 src/undate/converters/grammars/gregorian_multilang.lark
 rename tests/test_converters/test_calendars/{test_gregorian.py => test_gregorian/test_gregorian_converter.py} (100%)
 create mode 100644 tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py

diff --git a/pyproject.toml b/pyproject.toml
index fcebbbd..e7b3e77 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -81,6 +81,12 @@ path = "src/undate/__init__.py"
 [tool.hatch.build.targets.sdist]
 include = ["src/undate/**/*.py", "src/undate/**/*.lark", "tests/**"]
 
+[tool.hatch.envs.codegen]
+dependencies = ["babel"]
+
+[tool.hatch.envs.codegen.scripts]
+generate = "python scripts/generate_gregorian_grammar.py"
+
 [tool.pytest.ini_options]
 pythonpath = "src/"
 markers = [
diff --git a/scripts/generate_gregorian_grammar.py b/scripts/generate_gregorian_grammar.py
new file mode 100644
index 0000000..87dd7d0
--- /dev/null
+++ b/scripts/generate_gregorian_grammar.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+
+from babel.dates import get_month_names
+
+
+languages = {
+    "rw": "Kinyarwanda",
+    "lg": "Ganda",
+    "ti": "Tigrinya",
+    "fr": "French",
+    "en": "English",
+}
+# for locale_code in ["fr_FR", "de_DE", "rw_rw", "ti_ET", "lg_UG"]:
+
+
+def main():
+    for lang, name in languages.items():
+        print(f"\n###  {name} (`{lang}`)")
+        for width in ["abbreviated", "wide"]:
+            print(
+                f"- {width}: " + ", ".join(get_month_names(width, locale=lang).values())
+            )
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/undate/converters/calendars/gregorian/__init__.py b/src/undate/converters/calendars/gregorian/__init__.py
new file mode 100644
index 0000000..f08896b
--- /dev/null
+++ b/src/undate/converters/calendars/gregorian/__init__.py
@@ -0,0 +1,3 @@
+from undate.converters.calendars.gregorian.converter import GregorianDateConverter
+
+__all__ = ["GregorianDateConverter"]
diff --git a/src/undate/converters/calendars/gregorian.py b/src/undate/converters/calendars/gregorian/converter.py
similarity index 100%
rename from src/undate/converters/calendars/gregorian.py
rename to src/undate/converters/calendars/gregorian/converter.py
diff --git a/src/undate/converters/calendars/gregorian/parser.py b/src/undate/converters/calendars/gregorian/parser.py
new file mode 100644
index 0000000..cfcea53
--- /dev/null
+++ b/src/undate/converters/calendars/gregorian/parser.py
@@ -0,0 +1,10 @@
+from lark import Lark
+
+from undate.converters import GRAMMAR_FILE_PATH
+
+grammar_path = GRAMMAR_FILE_PATH / "gregorian.lark"
+
+# open based on filename to allow relative imports based on grammar file
+gregorian_parser = Lark.open(
+    str(grammar_path), rel_to=__file__, start="gregorian_date", strict=True
+)
diff --git a/src/undate/converters/calendars/gregorian/transformer.py b/src/undate/converters/calendars/gregorian/transformer.py
new file mode 100644
index 0000000..7f24e02
--- /dev/null
+++ b/src/undate/converters/calendars/gregorian/transformer.py
@@ -0,0 +1,37 @@
+from lark import Transformer, Tree
+
+from undate import Undate, Calendar
+
+
+class GregorianDateTransformer(Transformer):
+    """Transform a Gregorian date parse tree and return an Undate."""
+
+    # Currently parser should not result in intervals
+
+    calendar = Calendar.GREGORIAN
+
+    def gregorian_date(self, items):
+        parts = {}
+        for child in items:
+            if child.data in ["year", "month", "day"]:
+                # in each case we expect one integer value;
+                # anonymous tokens convert to their value and cast as int
+                value = int(child.children[0])
+                parts[str(child.data)] = value
+
+        # initialize and return an undate with year, month, day and
+        # Gregorian calendar
+        return Undate(**parts, calendar=self.calendar)
+
+    def year(self, items):
+        # combine multiple parts into a single string
+        value = "".join([str(i) for i in items])
+        return Tree(data="year", children=[value])
+
+    def month(self, items):
+        # month has a nested tree for the rule and the value
+        # the name of the rule (month_1, month_2, etc) gives us the
+        # number of the month needed for converting the date
+        tree = items[0]
+        month_n = tree.data.split("_")[-1]
+        return Tree(data="month", children=[month_n])
diff --git a/src/undate/converters/grammars/gregorian.lark b/src/undate/converters/grammars/gregorian.lark
new file mode 100644
index 0000000..308aee8
--- /dev/null
+++ b/src/undate/converters/grammars/gregorian.lark
@@ -0,0 +1,30 @@
+%import common.WS
+%ignore WS
+
+%import .gregorian_multilang (month_1, month_2)
+
+// no weekday support for now
+gregorian_date: day month year | month day year | year month day | month year | year month | year | day month | month day 
+
+// months have 29 to  30 days; we do not expect leading zeroes
+day: /[1-9]/ | /[12][0-9]/ | /3[0-1]/
+
+// Gregorian calendar started in 1582; assume years with 3 or more digits for now,
+// so we can support mixed day / year order unambiguously
+year: /\d{3,}/
+
+// months
+month: month_1
+     | month_2
+
+     // | month_3
+     // | month_4
+     // | month_5
+     // | month_6
+     // | month_7
+     // | month_8
+     // | month_9
+     // | month_10
+     // | month_11
+     // | month_12
+
diff --git a/src/undate/converters/grammars/gregorian_multilang.lark b/src/undate/converters/grammars/gregorian_multilang.lark
new file mode 100644
index 0000000..42e59bf
--- /dev/null
+++ b/src/undate/converters/grammars/gregorian_multilang.lark
@@ -0,0 +1,4 @@
+
+
+month_1: "Jan" | "January"
+month_2: "Feb" | "February"
\ No newline at end of file
diff --git a/tests/test_converters/test_calendars/test_gregorian.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
similarity index 100%
rename from tests/test_converters/test_calendars/test_gregorian.py
rename to tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
new file mode 100644
index 0000000..83df118
--- /dev/null
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
@@ -0,0 +1,52 @@
+import pytest
+from lark.exceptions import UnexpectedCharacters, UnexpectedEOF
+
+from undate.converters.calendars.gregorian.parser import gregorian_parser
+
+
+# for now, just test that valid dates can be parsed
+
+testcases = [
+    # year
+    "2012",
+    # month + year
+    "Jan 1960",
+    "Feb 1801",
+    "1900 Feb",
+    # day + month + year
+    "Feb 5 1602",
+    # "1602 February 5",
+    # day + month
+    "January 5",
+    "5 Jan",
+    # three digit year
+]
+
+
+@pytest.mark.parametrize("date_string", testcases)
+def test_should_parse(date_string):
+    assert gregorian_parser.parse(date_string)
+
+
+error_cases = [
+    # # invalid days
+    ("0 Tammuz 5403", UnexpectedCharacters),
+    # ("31 Tishri 5403", UnexpectedCharacters),
+    # # month alone
+    # ("Tishri", UnexpectedEOF),
+    # # month day only
+    ("12 ", UnexpectedEOF),
+    # # invalid month
+    # ("Foo 383", UnexpectedCharacters),
+    # # wrong format
+    # ("2024-10-02", UnexpectedCharacters),
+    # # year month day not supported
+    # ("5403 Adar", UnexpectedCharacters),
+    # ("5403 Adar 14", UnexpectedCharacters),
+]
+
+
+@pytest.mark.parametrize("date_string,exception", error_cases)
+def test_should_error(date_string, exception):
+    with pytest.raises(exception):
+        gregorian_parser.parse(date_string)

From 3c58c2e2a1246c74e08cd9c946215f591436dd2d Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 13:37:36 -0500
Subject: [PATCH 02/17] Fully implement script to generate month names for
 Gregorian parser

---
 scripts/generate_gregorian_grammar.py | 62 +++++++++++++++++++++------
 1 file changed, 48 insertions(+), 14 deletions(-)

diff --git a/scripts/generate_gregorian_grammar.py b/scripts/generate_gregorian_grammar.py
index 87dd7d0..9b5f770 100644
--- a/scripts/generate_gregorian_grammar.py
+++ b/scripts/generate_gregorian_grammar.py
@@ -1,25 +1,59 @@
 #!/usr/bin/env python
 
+from collections import defaultdict
+import pathlib
+
 from babel.dates import get_month_names
 
+# lark grammar path relative to this script
+GRAMMAR_DIR_PATH = (
+    pathlib.Path(__file__).parent.parent / "src" / "undate" / "converters" / "grammars"
+)
+# file that is generated by this script, in that directory
+MONTH_GRAMMAR_FILE = GRAMMAR_DIR_PATH / "gregorian_multilang.lark"
+
+# include month names in the following languages
+languages = [
+    "en",  # English
+    "es",  # Spanish
+    "fr",  # French
+    "de",  # German
+    "rw",  # Kinyarwanda
+    "lg",  # Ganda
+    "ti",  # Tigrinya
+]
 
-languages = {
-    "rw": "Kinyarwanda",
-    "lg": "Ganda",
-    "ti": "Tigrinya",
-    "fr": "French",
-    "en": "English",
-}
-# for locale_code in ["fr_FR", "de_DE", "rw_rw", "ti_ET", "lg_UG"]:
+# warning to include at top of generated file
+warning_text = """// WARNING: This file is auto-generated. DO NOT EDIT.
+// To regenerate: uvx hatch run codegen:generate
+
+"""
 
 
 def main():
-    for lang, name in languages.items():
-        print(f"\n###  {name} (`{lang}`)")
-        for width in ["abbreviated", "wide"]:
-            print(
-                f"- {width}: " + ", ".join(get_month_names(width, locale=lang).values())
-            )
+    # create a dictionary of lists to hold the names for each month
+    all_month_names = defaultdict(list)
+
+    for lang in languages:
+        for width in ["wide", "abbreviated"]:
+            for month_num, month_name in get_month_names(width, locale=lang).items():
+                # some locales use a . on the shortened month; let's ignore that
+                all_month_names[month_num].append(month_name.strip("."))
+
+    with MONTH_GRAMMAR_FILE.open("w") as outfile:
+        outfile.write(warning_text)
+
+        # for each numeric month, generate a rule with all variant names:
+        # month_1:  "January" | "Jan"  ...
+        for i, names in all_month_names.items():
+            # combine all names in an OR string
+            or_names = " | ".join(f'"{m}"' for m in names)
+            outfile.write(f"month_{i}: {or_names}\n")
+
+    print(
+        f"Successfully regenerated {MONTH_GRAMMAR_FILE.relative_to(pathlib.Path.cwd())}"
+    )
+    print("If the file has changed, make sure to commit the new version.")
 
 
 if __name__ == "__main__":

From 01ebe5e93ea75c4b9e79dc12a15fcf59b5263b0e Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 13:38:04 -0500
Subject: [PATCH 03/17] Grammar with month names in multiple languages

---
 .../grammars/gregorian_multilang.lark           | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/undate/converters/grammars/gregorian_multilang.lark b/src/undate/converters/grammars/gregorian_multilang.lark
index 42e59bf..6505be7 100644
--- a/src/undate/converters/grammars/gregorian_multilang.lark
+++ b/src/undate/converters/grammars/gregorian_multilang.lark
@@ -1,4 +1,15 @@
+// WARNING: This file is auto-generated. DO NOT EDIT.
+// To regenerate: uvx hatch run codegen:generate
 
-
-month_1: "Jan" | "January"
-month_2: "Feb" | "February"
\ No newline at end of file
+month_1: "January" | "Jan" | "enero" | "ene" | "janvier" | "janv" | "Januar" | "Jan" | "Mutarama" | "mut" | "Janwaliyo" | "Jan" | "ጥሪ" | "ጥሪ"
+month_2: "February" | "Feb" | "febrero" | "feb" | "février" | "févr" | "Februar" | "Feb" | "Gashyantare" | "gas" | "Febwaliyo" | "Feb" | "ለካቲት" | "ለካ"
+month_3: "March" | "Mar" | "marzo" | "mar" | "mars" | "mars" | "März" | "März" | "Werurwe" | "wer" | "Marisi" | "Mar" | "መጋቢት" | "መጋ"
+month_4: "April" | "Apr" | "abril" | "abr" | "avril" | "avr" | "April" | "Apr" | "Mata" | "mat" | "Apuli" | "Apu" | "ሚያዝያ" | "ሚያ"
+month_5: "May" | "May" | "mayo" | "may" | "mai" | "mai" | "Mai" | "Mai" | "Gicurasi" | "gic" | "Maayi" | "Maa" | "ጉንበት" | "ግን"
+month_6: "June" | "Jun" | "junio" | "jun" | "juin" | "juin" | "Juni" | "Juni" | "Kamena" | "kam" | "Juuni" | "Juu" | "ሰነ" | "ሰነ"
+month_7: "July" | "Jul" | "julio" | "jul" | "juillet" | "juil" | "Juli" | "Juli" | "Nyakanga" | "nya" | "Julaayi" | "Jul" | "ሓምለ" | "ሓም"
+month_8: "August" | "Aug" | "agosto" | "ago" | "août" | "août" | "August" | "Aug" | "Kanama" | "kan" | "Agusito" | "Agu" | "ነሓሰ" | "ነሓ"
+month_9: "September" | "Sep" | "septiembre" | "sept" | "septembre" | "sept" | "September" | "Sept" | "Nzeri" | "nze" | "Sebuttemba" | "Seb" | "መስከረም" | "መስ"
+month_10: "October" | "Oct" | "octubre" | "oct" | "octobre" | "oct" | "Oktober" | "Okt" | "Ukwakira" | "ukw" | "Okitobba" | "Oki" | "ጥቅምቲ" | "ጥቅ"
+month_11: "November" | "Nov" | "noviembre" | "nov" | "novembre" | "nov" | "November" | "Nov" | "Ugushyingo" | "ugu" | "Novemba" | "Nov" | "ሕዳር" | "ሕዳ"
+month_12: "December" | "Dec" | "diciembre" | "dic" | "décembre" | "déc" | "Dezember" | "Dez" | "Ukuboza" | "uku" | "Desemba" | "Des" | "ታሕሳስ" | "ታሕ"

From fb2906125acc99273437fed0cba1ff52289918b3 Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 13:39:36 -0500
Subject: [PATCH 04/17] Import and use all month names

---
 src/undate/converters/grammars/gregorian.lark | 28 +++++++++----------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/undate/converters/grammars/gregorian.lark b/src/undate/converters/grammars/gregorian.lark
index 308aee8..b30a594 100644
--- a/src/undate/converters/grammars/gregorian.lark
+++ b/src/undate/converters/grammars/gregorian.lark
@@ -1,12 +1,13 @@
 %import common.WS
 %ignore WS
 
-%import .gregorian_multilang (month_1, month_2)
+%import .gregorian_multilang (month_1, month_2, month_3, month_4, month_5,  \
+	month_6, month_7, month_8, month_9, month_10, month_11, month_12)
 
 // no weekday support for now
 gregorian_date: day month year | month day year | year month day | month year | year month | year | day month | month day 
 
-// months have 29 to  30 days; we do not expect leading zeroes
+// months have 28 to 31 days; we do not expect leading zeroes
 day: /[1-9]/ | /[12][0-9]/ | /3[0-1]/
 
 // Gregorian calendar started in 1582; assume years with 3 or more digits for now,
@@ -15,16 +16,15 @@ year: /\d{3,}/
 
 // months
 month: month_1
-     | month_2
-
-     // | month_3
-     // | month_4
-     // | month_5
-     // | month_6
-     // | month_7
-     // | month_8
-     // | month_9
-     // | month_10
-     // | month_11
-     // | month_12
+    | month_2
+    | month_3
+    | month_4
+    | month_5
+    | month_6
+    | month_7
+    | month_8
+    | month_9
+    | month_10
+    | month_11
+    | month_12
 

From 6d6259b50cab0b20dae30a204257ce14a7c77157 Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 13:46:41 -0500
Subject: [PATCH 05/17] Don't repeat month names / abbreviations

---
 scripts/generate_gregorian_grammar.py         |  7 +++++-
 .../grammars/gregorian_multilang.lark         | 22 +++++++++----------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/scripts/generate_gregorian_grammar.py b/scripts/generate_gregorian_grammar.py
index 9b5f770..a5f4563 100644
--- a/scripts/generate_gregorian_grammar.py
+++ b/scripts/generate_gregorian_grammar.py
@@ -38,7 +38,12 @@ def main():
         for width in ["wide", "abbreviated"]:
             for month_num, month_name in get_month_names(width, locale=lang).items():
                 # some locales use a . on the shortened month; let's ignore that
-                all_month_names[month_num].append(month_name.strip("."))
+                month_name = month_name.strip(".")
+                # In some cases different languages have the same abbreviations;
+                # in some cases, abbreviated and full are the same.
+                # Only add if not already present, to avoid redundancy
+                if month_name not in all_month_names[month_num]:
+                    all_month_names[month_num].append(month_name)
 
     with MONTH_GRAMMAR_FILE.open("w") as outfile:
         outfile.write(warning_text)
diff --git a/src/undate/converters/grammars/gregorian_multilang.lark b/src/undate/converters/grammars/gregorian_multilang.lark
index 6505be7..83dcbb1 100644
--- a/src/undate/converters/grammars/gregorian_multilang.lark
+++ b/src/undate/converters/grammars/gregorian_multilang.lark
@@ -1,15 +1,15 @@
 // WARNING: This file is auto-generated. DO NOT EDIT.
 // To regenerate: uvx hatch run codegen:generate
 
-month_1: "January" | "Jan" | "enero" | "ene" | "janvier" | "janv" | "Januar" | "Jan" | "Mutarama" | "mut" | "Janwaliyo" | "Jan" | "ጥሪ" | "ጥሪ"
-month_2: "February" | "Feb" | "febrero" | "feb" | "février" | "févr" | "Februar" | "Feb" | "Gashyantare" | "gas" | "Febwaliyo" | "Feb" | "ለካቲት" | "ለካ"
-month_3: "March" | "Mar" | "marzo" | "mar" | "mars" | "mars" | "März" | "März" | "Werurwe" | "wer" | "Marisi" | "Mar" | "መጋቢት" | "መጋ"
-month_4: "April" | "Apr" | "abril" | "abr" | "avril" | "avr" | "April" | "Apr" | "Mata" | "mat" | "Apuli" | "Apu" | "ሚያዝያ" | "ሚያ"
-month_5: "May" | "May" | "mayo" | "may" | "mai" | "mai" | "Mai" | "Mai" | "Gicurasi" | "gic" | "Maayi" | "Maa" | "ጉንበት" | "ግን"
-month_6: "June" | "Jun" | "junio" | "jun" | "juin" | "juin" | "Juni" | "Juni" | "Kamena" | "kam" | "Juuni" | "Juu" | "ሰነ" | "ሰነ"
-month_7: "July" | "Jul" | "julio" | "jul" | "juillet" | "juil" | "Juli" | "Juli" | "Nyakanga" | "nya" | "Julaayi" | "Jul" | "ሓምለ" | "ሓም"
-month_8: "August" | "Aug" | "agosto" | "ago" | "août" | "août" | "August" | "Aug" | "Kanama" | "kan" | "Agusito" | "Agu" | "ነሓሰ" | "ነሓ"
-month_9: "September" | "Sep" | "septiembre" | "sept" | "septembre" | "sept" | "September" | "Sept" | "Nzeri" | "nze" | "Sebuttemba" | "Seb" | "መስከረም" | "መስ"
-month_10: "October" | "Oct" | "octubre" | "oct" | "octobre" | "oct" | "Oktober" | "Okt" | "Ukwakira" | "ukw" | "Okitobba" | "Oki" | "ጥቅምቲ" | "ጥቅ"
-month_11: "November" | "Nov" | "noviembre" | "nov" | "novembre" | "nov" | "November" | "Nov" | "Ugushyingo" | "ugu" | "Novemba" | "Nov" | "ሕዳር" | "ሕዳ"
+month_1: "January" | "Jan" | "enero" | "ene" | "janvier" | "janv" | "Januar" | "Mutarama" | "mut" | "Janwaliyo" | "ጥሪ"
+month_2: "February" | "Feb" | "febrero" | "feb" | "février" | "févr" | "Februar" | "Gashyantare" | "gas" | "Febwaliyo" | "ለካቲት" | "ለካ"
+month_3: "March" | "Mar" | "marzo" | "mar" | "mars" | "März" | "Werurwe" | "wer" | "Marisi" | "መጋቢት" | "መጋ"
+month_4: "April" | "Apr" | "abril" | "abr" | "avril" | "avr" | "Mata" | "mat" | "Apuli" | "Apu" | "ሚያዝያ" | "ሚያ"
+month_5: "May" | "mayo" | "may" | "mai" | "Mai" | "Gicurasi" | "gic" | "Maayi" | "Maa" | "ጉንበት" | "ግን"
+month_6: "June" | "Jun" | "junio" | "jun" | "juin" | "Juni" | "Kamena" | "kam" | "Juuni" | "Juu" | "ሰነ"
+month_7: "July" | "Jul" | "julio" | "jul" | "juillet" | "juil" | "Juli" | "Nyakanga" | "nya" | "Julaayi" | "ሓምለ" | "ሓም"
+month_8: "August" | "Aug" | "agosto" | "ago" | "août" | "Kanama" | "kan" | "Agusito" | "Agu" | "ነሓሰ" | "ነሓ"
+month_9: "September" | "Sep" | "septiembre" | "sept" | "septembre" | "Sept" | "Nzeri" | "nze" | "Sebuttemba" | "Seb" | "መስከረም" | "መስ"
+month_10: "October" | "Oct" | "octubre" | "oct" | "octobre" | "Oktober" | "Okt" | "Ukwakira" | "ukw" | "Okitobba" | "Oki" | "ጥቅምቲ" | "ጥቅ"
+month_11: "November" | "Nov" | "noviembre" | "nov" | "novembre" | "Ugushyingo" | "ugu" | "Novemba" | "ሕዳር" | "ሕዳ"
 month_12: "December" | "Dec" | "diciembre" | "dic" | "décembre" | "déc" | "Dezember" | "Dez" | "Ukuboza" | "uku" | "Desemba" | "Des" | "ታሕሳስ" | "ታሕ"

From 294e573ee283d292a198884ed8ec659a75578a8c Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 13:52:59 -0500
Subject: [PATCH 06/17] Add more test cases in multiple languages

---
 .../test_gregorian/test_gregorian_parser.py   | 58 ++++++++++++-------
 1 file changed, 38 insertions(+), 20 deletions(-)

diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
index 83df118..f4f5af8 100644
--- a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
@@ -4,22 +4,40 @@
 from undate.converters.calendars.gregorian.parser import gregorian_parser
 
 
-# for now, just test that valid dates can be parsed
+# test that valid dates can be parsed to confirm parser is working correctly
 
 testcases = [
     # year
     "2012",
+    # three digit year
+    "566",
     # month + year
     "Jan 1960",
     "Feb 1801",
     "1900 Feb",
-    # day + month + year
-    "Feb 5 1602",
-    # "1602 February 5",
+    # day + month + year in any order
+    "May 5 1602",
+    "5 May 1602",
+    "1602 October 5",
     # day + month
-    "January 5",
-    "5 Jan",
-    # three digit year
+    "December 5",
+    "5 December",
+    # Kinyarwanda (rw)
+    "2025 ugu 4",  # Babel renders as "2025 ugu. 4"
+    "2025 Ugushyingo 4",
+    "2025 ugu",
+    "2025 Ugushyingo",
+    # Ganda (lg)
+    "4 Novemba 2025",
+    "4 Nov 2025",
+    "Novemba 2025",
+    "4 Novemba",
+    # Tigrinya (ti)
+    "ሕዳ 4 2025",  # Babel renders with a comma after the day
+    "ሕዳር 4 2025",
+    # French
+    "18 avril 2025",
+    "18 avr 2025",  # Babel renders as 18 avr. 2025
 ]
 
 
@@ -29,20 +47,20 @@ def test_should_parse(date_string):
 
 
 error_cases = [
-    # # invalid days
-    ("0 Tammuz 5403", UnexpectedCharacters),
-    # ("31 Tishri 5403", UnexpectedCharacters),
-    # # month alone
-    # ("Tishri", UnexpectedEOF),
-    # # month day only
+    # invalid days
+    ("0 June 1006", UnexpectedCharacters),
+    ("42 March 1206", UnexpectedCharacters),
+    # month alone
+    ("Juin", UnexpectedCharacters),
+    # day only
     ("12 ", UnexpectedEOF),
-    # # invalid month
-    # ("Foo 383", UnexpectedCharacters),
-    # # wrong format
-    # ("2024-10-02", UnexpectedCharacters),
-    # # year month day not supported
-    # ("5403 Adar", UnexpectedCharacters),
-    # ("5403 Adar 14", UnexpectedCharacters),
+    # non-Gregorian month
+    ("5 Tammuz 5403", UnexpectedCharacters),
+    ("31 Tishri 5403", UnexpectedCharacters),
+    # invalid month
+    ("Foo 383", UnexpectedCharacters),
+    # wrong format
+    ("2024-10-02", UnexpectedCharacters),
 ]
 
 

From f654e830d241ee9629146072cc6a53b37cf3320b Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 14:12:28 -0500
Subject: [PATCH 07/17] Test gregorian parser transformer; refine parsing logic

---
 src/undate/converters/grammars/gregorian.lark | 10 +++++-
 .../test_gregorian/test_gregorian_parser.py   |  6 ++--
 .../test_gregorian_transformer.py             | 31 +++++++++++++++++++
 3 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_converters/test_calendars/test_gregorian/test_gregorian_transformer.py

diff --git a/src/undate/converters/grammars/gregorian.lark b/src/undate/converters/grammars/gregorian.lark
index b30a594..d70b0db 100644
--- a/src/undate/converters/grammars/gregorian.lark
+++ b/src/undate/converters/grammars/gregorian.lark
@@ -1,9 +1,15 @@
 %import common.WS
 %ignore WS
 
+// Some abbreviations use periods; some default date formats
+// include commas. Ignore both
+PUNCTUATION: "." | ","
+%ignore PUNCTUATION
+
 %import .gregorian_multilang (month_1, month_2, month_3, month_4, month_5,  \
 	month_6, month_7, month_8, month_9, month_10, month_11, month_12)
 
+
 // no weekday support for now
 gregorian_date: day month year | month day year | year month day | month year | year month | year | day month | month day 
 
@@ -12,7 +18,9 @@ day: /[1-9]/ | /[12][0-9]/ | /3[0-1]/
 
 // Gregorian calendar started in 1582; assume years with 3 or more digits for now,
 // so we can support mixed day / year order unambiguously
-year: /\d{3,}/
+year: /\b\d{3,}\b/
+// Use word boundaries to separate from other tokens (esp. numeric day), 
+// since we otherwise ignore whitespace
 
 // months
 month: month_1
diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
index f4f5af8..6cb7ba6 100644
--- a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
@@ -23,7 +23,7 @@
     "December 5",
     "5 December",
     # Kinyarwanda (rw)
-    "2025 ugu 4",  # Babel renders as "2025 ugu. 4"
+    "2025 ugu. 4",
     "2025 Ugushyingo 4",
     "2025 ugu",
     "2025 Ugushyingo",
@@ -33,11 +33,11 @@
     "Novemba 2025",
     "4 Novemba",
     # Tigrinya (ti)
-    "ሕዳ 4 2025",  # Babel renders with a comma after the day
+    "ሕዳ 4, 2025",
     "ሕዳር 4 2025",
     # French
     "18 avril 2025",
-    "18 avr 2025",  # Babel renders as 18 avr. 2025
+    "18 avr. 2025",
 ]
 
 
diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_transformer.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_transformer.py
new file mode 100644
index 0000000..114a713
--- /dev/null
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_transformer.py
@@ -0,0 +1,31 @@
+import pytest
+from undate.converters.calendars.gregorian.parser import gregorian_parser
+from undate.converters.calendars.gregorian.transformer import GregorianDateTransformer
+from undate.undate import Undate, Calendar
+from undate.date import DatePrecision
+
+
+testcases = [
+    ("2012", Undate(2012), DatePrecision.YEAR),
+    ("May 13 1602", Undate(1602, 5, 13), DatePrecision.DAY),
+    ("Jan 1960", Undate(1960, 1), DatePrecision.MONTH),
+    ("2022 ugu. 4", Undate(2022, 11, 4), DatePrecision.DAY),
+    ("2022 Ugushyingo", Undate(2022, 11), DatePrecision.MONTH),
+    ("4 Novemba", Undate(month=11, day=4), DatePrecision.DAY),
+    # ignores whitespace, comma, period
+    ("4Novemba", Undate(month=11, day=4), DatePrecision.DAY),
+    ("18 avril, 2025", Undate(2025, 4, 18), DatePrecision.DAY),
+]
+
+
+@pytest.mark.parametrize("date_string,expected,expected_precision", testcases)
+def test_transform(date_string, expected, expected_precision):
+    transformer = GregorianDateTransformer(visit_tokens=True)
+    # parse the input string, then transform to undate object
+    parsetree = gregorian_parser.parse(date_string)
+    transformed_date = transformer.transform(parsetree)
+    # use EDTF to compare so we can check dates with unknown years
+    assert transformed_date.format("EDTF") == expected.format("EDTF")
+    # currently only returns undate, parser doesn't support intervals
+    assert transformed_date.precision == expected_precision
+    assert transformed_date.calendar == Calendar.GREGORIAN

From 5b5d89f0e6246ac428b1af4e80504d3b8a395c3c Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 14:20:21 -0500
Subject: [PATCH 08/17] Connect parsing to gregorian converter class and test

---
 .../calendars/gregorian/converter.py          | 30 +++++++++++++++++++
 .../test_gregorian_converter.py               | 27 +++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/src/undate/converters/calendars/gregorian/converter.py b/src/undate/converters/calendars/gregorian/converter.py
index b3b103b..30e2dfc 100644
--- a/src/undate/converters/calendars/gregorian/converter.py
+++ b/src/undate/converters/calendars/gregorian/converter.py
@@ -1,6 +1,11 @@
 from calendar import monthrange, isleap
 
+from lark.exceptions import UnexpectedCharacters
+
+from undate.undate import Undate
 from undate.converters.base import BaseCalendarConverter
+from undate.converters.calendars.gregorian.parser import gregorian_parser
+from undate.converters.calendars.gregorian.transformer import GregorianDateTransformer
 
 
 class GregorianDateConverter(BaseCalendarConverter):
@@ -18,6 +23,9 @@ class GregorianDateConverter(BaseCalendarConverter):
     #: arbitrary known leap year
     LEAP_YEAR: int = 2024
 
+    def __init__(self):
+        self.transformer = GregorianDateTransformer()
+
     def min_month(self) -> int:
         """First month for the Gregorian calendar."""
         return 1
@@ -79,3 +87,25 @@ def to_gregorian(self, year, month, day) -> tuple[int, int, int]:
         a common point of comparison.
         """
         return (year, month, day)
+
+    def parse(self, value: str) -> Undate:
+        """
+        Parse a Gregorian date string of any supported precision in any
+        supported language and return an :class:`~undate.undate.Undate`.
+        The input date string is preserved in the label of the resulting
+        Undate object.
+        """
+        if not value:
+            raise ValueError("Parsing empty string is not supported")
+
+        # parse the input string, then transform to undate object
+        try:
+            # parse the string with our Hebrew date parser
+            parsetree = gregorian_parser.parse(value)
+            # transform the parse tree into an undate object
+            undate_obj = self.transformer.transform(parsetree)
+            # set the original date string as the label
+            undate_obj.label = value
+            return undate_obj
+        except UnexpectedCharacters as err:
+            raise ValueError(f"Could not parse '{value}' as a Gregorian date") from err
diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
index e0bf5ef..f506d23 100644
--- a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
@@ -1,3 +1,5 @@
+from undate.date import DatePrecision
+from undate.undate import Undate, Calendar
 from undate.converters.calendars import GregorianDateConverter
 
 
@@ -38,3 +40,28 @@ def test_representative_years(self):
             converter.LEAP_YEAR,
             converter.NON_LEAP_YEAR,
         ]
+
+    def test_parse(self):
+        # day
+        date_str = "2022 Ugushyingo 26"
+        date = GregorianDateConverter().parse(date_str)
+        assert date == Undate(2022, 11, 26)  # Ugushyingo = November
+        assert date.calendar == Calendar.GREGORIAN
+        assert date.precision == DatePrecision.DAY
+        assert date.label == date_str
+
+        # month
+        date_str = "avril 1362"
+        date = GregorianDateConverter().parse(date_str)
+        assert date == Undate(1362, 4)
+        assert date.calendar == Calendar.GREGORIAN
+        assert date.precision == DatePrecision.MONTH
+        assert date.label == date_str
+
+        # year
+        date_str = "932"
+        date = GregorianDateConverter().parse(date_str)
+        assert date == Undate(932)
+        assert date.calendar == Calendar.GREGORIAN
+        assert date.precision == DatePrecision.YEAR
+        assert date.label == date_str

From 6600f58d0f89a69df79926edc08b65705546956f Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 14:38:14 -0500
Subject: [PATCH 09/17] Add Gregorian to omnibus parser

---
 .../calendars/gregorian/transformer.py         |  5 +++++
 src/undate/converters/combined.py              |  4 +++-
 src/undate/converters/grammars/combined.lark   | 18 +++++++++++++++---
 src/undate/converters/grammars/gregorian.lark  |  6 +++---
 tests/test_converters/test_combined_parser.py  |  5 +++++
 5 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/undate/converters/calendars/gregorian/transformer.py b/src/undate/converters/calendars/gregorian/transformer.py
index 7f24e02..a8e7048 100644
--- a/src/undate/converters/calendars/gregorian/transformer.py
+++ b/src/undate/converters/calendars/gregorian/transformer.py
@@ -35,3 +35,8 @@ def month(self, items):
         tree = items[0]
         month_n = tree.data.split("_")[-1]
         return Tree(data="month", children=[month_n])
+
+    def day(self, items):
+        # combine multiple parts into a single string
+        value = "".join([str(i) for i in items])
+        return Tree(data="day", children=[value])
diff --git a/src/undate/converters/combined.py b/src/undate/converters/combined.py
index 54d66a5..c74beb9 100644
--- a/src/undate/converters/combined.py
+++ b/src/undate/converters/combined.py
@@ -13,6 +13,7 @@
 from undate import Undate, UndateInterval
 from undate.converters import BaseDateConverter, GRAMMAR_FILE_PATH
 from undate.converters.edtf.transformer import EDTFTransformer
+from undate.converters.calendars.gregorian.transformer import GregorianDateTransformer
 from undate.converters.calendars.hebrew.transformer import HebrewDateTransformer
 from undate.converters.calendars.islamic.transformer import IslamicDateTransformer
 
@@ -33,6 +34,7 @@ def start(self, children):
     edtf=EDTFTransformer(),
     hebrew=HebrewDateTransformer(),
     islamic=IslamicDateTransformer(),
+    gregorian=GregorianDateTransformer(),
 )
 
 
@@ -45,7 +47,7 @@ def start(self, children):
 class OmnibusDateConverter(BaseDateConverter):
     """
     Combination parser that aggregates existing parser grammars.
-    Currently supports EDTF, Hebrew, and Hijri  where dates are unambiguous.
+    Currently supports EDTF, Gregorian, Hebrew, and Hijri where dates are unambiguous.
     (Year-only dates are parsed as EDTF in Gregorian calendar.)
 
     Does not support serialization.
diff --git a/src/undate/converters/grammars/combined.lark b/src/undate/converters/grammars/combined.lark
index 0e77b5c..1f87208 100644
--- a/src/undate/converters/grammars/combined.lark
+++ b/src/undate/converters/grammars/combined.lark
@@ -1,7 +1,12 @@
 %import common.WS
 %ignore WS
 
-start: (edtf__start | hebrew__hebrew_date  | islamic__islamic_date )
+// Some abbreviations use periods; some default date formats
+// include commas. Ignore both. (Copied from gregorian.lark)
+PUNCTUATION: "." | ","
+%ignore PUNCTUATION
+
+start: (edtf__start | hebrew__hebrew_date  | islamic__islamic_date | gregorian__gregorian_date )
 
 // Renaming of the import variables is required, as they receive the namespace of this file.
 // See: https://github.com/lark-parser/lark/pull/973#issuecomment-907287565
@@ -23,10 +28,17 @@ start: (edtf__start | hebrew__hebrew_date  | islamic__islamic_date )
 %import .islamic.month -> islamic__month
 %import .islamic.year -> islamic__year
 
+// gregorian calendar, in multiple languages
+%import .gregorian.gregorian_date -> gregorian__gregorian_date
+
 
 // override hebrew date to omit year-only, since year without calendar is ambiguous
 // NOTE: potentially support year with calendar label
-%override hebrew__hebrew_date: hebrew__day hebrew__month hebrew__year | hebrew__month hebrew__year 
+%override hebrew__hebrew_date: hebrew__day hebrew__month hebrew__year | hebrew__month hebrew__year
 
 // same for islamic date, year alone is ambiguous
-%override islamic__islamic_date: islamic__day islamic__month islamic__year | islamic__month islamic__year 
+%override islamic__islamic_date: islamic__day islamic__month islamic__year | islamic__month islamic__year
+
+// same as above. omit year only, since covered by EDTF
+// %override gregorian__gregorian_date: day month year | month day year | year month day | month year | year month |  day month | month day
+
diff --git a/src/undate/converters/grammars/gregorian.lark b/src/undate/converters/grammars/gregorian.lark
index d70b0db..74cff9b 100644
--- a/src/undate/converters/grammars/gregorian.lark
+++ b/src/undate/converters/grammars/gregorian.lark
@@ -11,15 +11,15 @@ PUNCTUATION: "." | ","
 
 
 // no weekday support for now
-gregorian_date: day month year | month day year | year month day | month year | year month | year | day month | month day 
+gregorian_date: day month year | month day year | year month day | month year | year month | year | day month | month day
 
 // months have 28 to 31 days; we do not expect leading zeroes
-day: /[1-9]/ | /[12][0-9]/ | /3[0-1]/
+day:  /[1-9]/ | /[12][0-9]/ | /3[0-1]/
 
 // Gregorian calendar started in 1582; assume years with 3 or more digits for now,
 // so we can support mixed day / year order unambiguously
 year: /\b\d{3,}\b/
-// Use word boundaries to separate from other tokens (esp. numeric day), 
+// Use word boundaries to separate from other tokens (esp. numeric day),
 // since we otherwise ignore whitespace
 
 // months
diff --git a/tests/test_converters/test_combined_parser.py b/tests/test_converters/test_combined_parser.py
index 717a16e..d6e0621 100644
--- a/tests/test_converters/test_combined_parser.py
+++ b/tests/test_converters/test_combined_parser.py
@@ -19,6 +19,11 @@
     ("Jumādā I 1243", Undate(1243, 5, calendar="Islamic")),
     ("7 Jumādā I 1243", Undate(1243, 5, 7, calendar="Islamic")),
     ("14 Rabīʿ I 901", Undate(901, 3, 14, calendar="Islamic")),
+    # Gregorian with non-numeric month (full or abbreviated)
+    ("June 1602", Undate(1602, 6, calendar="Gregorian")),
+    ("13 Jan 1602", Undate(1602, 1, 13, calendar="Gregorian")),
+    ("2022 ugu. 4", Undate(2022, 11, 4, calendar="Gregorian")),
+    ("18 avril", Undate(month=4, day=18, calendar="Gregorian")),
 ]
 
 

From 2bd8c23cd32435cd76788aefd0257ada645622ad Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 14:41:59 -0500
Subject: [PATCH 10/17] Document Gregorian parser & languages in change log

---
 CHANGELOG.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 51746ff..5375a5b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Change Log
 
+## 0.7
+
+- Add parsing to Gregorian date converter; supports month names (full or abbreviated)
+  in English, French, German, Spanish, Kinyarwanda, Ganda, and Tigrinya
+- Include Gregorian dates in omnibus parser
+
 ## 0.6
 
 - Experimental omnibus date converter + parser (EDTF, Hebrew, Hijri)

From 9ca84244068960fbdad55d6f99c0e30de71d85cc Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 14:59:27 -0500
Subject: [PATCH 11/17] Add dev notes for codegen script; drop uvx from hatch
 run command

---
 DEVELOPER_NOTES.md                              | 17 ++++++++++++++++-
 scripts/generate_gregorian_grammar.py           | 12 +++++++++++-
 .../grammars/gregorian_multilang.lark           |  2 +-
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/DEVELOPER_NOTES.md b/DEVELOPER_NOTES.md
index 6d4918c..e74c145 100644
--- a/DEVELOPER_NOTES.md
+++ b/DEVELOPER_NOTES.md
@@ -88,4 +88,19 @@ pip install -e ".[docs]"
 sphinx-build docs docs/_build
 ```
 
-HTML documentation will be generated in `docs/_build/html`
\ No newline at end of file
+HTML documentation will be generated in `docs/_build/html`
+
+
+### Regenerating multilingual Gregorian month name parse file
+
+The Gregorian Lark parser includes a script-generated file, which
+populates month names based on a list of language codes using the Babel
+library.  To regenerate, run the script with hatch (which should
+be installed globally)::
+
+    hatch run codegen:generate
+    
+When the `.lark` file is modified by the script, it must be committed to git.
+
+
+
diff --git a/scripts/generate_gregorian_grammar.py b/scripts/generate_gregorian_grammar.py
index a5f4563..ce68362 100644
--- a/scripts/generate_gregorian_grammar.py
+++ b/scripts/generate_gregorian_grammar.py
@@ -1,4 +1,14 @@
 #!/usr/bin/env python
+"""
+This script generates the gregorian_multilang.lark file
+with month names (full and abbreviated) based on the list of
+target languages.
+
+Run this script with hatch to regeneate the file::
+
+    hatch run codegen:generate
+
+"""
 
 from collections import defaultdict
 import pathlib
@@ -25,7 +35,7 @@
 
 # warning to include at top of generated file
 warning_text = """// WARNING: This file is auto-generated. DO NOT EDIT.
-// To regenerate: uvx hatch run codegen:generate
+// To regenerate: hatch run codegen:generate
 
 """
 
diff --git a/src/undate/converters/grammars/gregorian_multilang.lark b/src/undate/converters/grammars/gregorian_multilang.lark
index 83dcbb1..a4d6045 100644
--- a/src/undate/converters/grammars/gregorian_multilang.lark
+++ b/src/undate/converters/grammars/gregorian_multilang.lark
@@ -1,5 +1,5 @@
 // WARNING: This file is auto-generated. DO NOT EDIT.
-// To regenerate: uvx hatch run codegen:generate
+// To regenerate: hatch run codegen:generate
 
 month_1: "January" | "Jan" | "enero" | "ene" | "janvier" | "janv" | "Januar" | "Mutarama" | "mut" | "Janwaliyo" | "ጥሪ"
 month_2: "February" | "Feb" | "febrero" | "feb" | "février" | "févr" | "Februar" | "Gashyantare" | "gas" | "Febwaliyo" | "ለካቲት" | "ለካ"

From e4c468dc2bd07597fd4989cdc8374d63ac41caa6 Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:17:15 -0500
Subject: [PATCH 12/17] Make Gregorian parser case-insensitive

---
 scripts/generate_gregorian_grammar.py         | 13 +++++-----
 .../calendars/gregorian/converter.py          |  2 +-
 .../grammars/gregorian_multilang.lark         | 24 +++++++++----------
 .../test_gregorian/test_gregorian_parser.py   |  5 +++-
 4 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/scripts/generate_gregorian_grammar.py b/scripts/generate_gregorian_grammar.py
index ce68362..822bbf7 100644
--- a/scripts/generate_gregorian_grammar.py
+++ b/scripts/generate_gregorian_grammar.py
@@ -4,7 +4,7 @@
 with month names (full and abbreviated) based on the list of
 target languages.
 
-Run this script with hatch to regeneate the file::
+Run this script with hatch to regenerate the file::
 
     hatch run codegen:generate
 
@@ -48,7 +48,7 @@ def main():
         for width in ["wide", "abbreviated"]:
             for month_num, month_name in get_month_names(width, locale=lang).items():
                 # some locales use a . on the shortened month; let's ignore that
-                month_name = month_name.strip(".")
+                month_name = month_name.strip(".").lower()
                 # In some cases different languages have the same abbreviations;
                 # in some cases, abbreviated and full are the same.
                 # Only add if not already present, to avoid redundancy
@@ -59,11 +59,12 @@ def main():
         outfile.write(warning_text)
 
         # for each numeric month, generate a rule with all variant names:
-        # month_1:  "January" | "Jan"  ...
+        # month_1:  /January|Jan/i
         for i, names in all_month_names.items():
-            # combine all names in an OR string
-            or_names = " | ".join(f'"{m}"' for m in names)
-            outfile.write(f"month_{i}: {or_names}\n")
+            # combine all names in a case-insensitive OR regex
+            # sort shortest variants last to avoid partial matches hitting first
+            or_names = "|".join(sorted(names, key=len, reverse=True))
+            outfile.write(f"month_{i}: /({or_names})/i\n")
 
     print(
         f"Successfully regenerated {MONTH_GRAMMAR_FILE.relative_to(pathlib.Path.cwd())}"
diff --git a/src/undate/converters/calendars/gregorian/converter.py b/src/undate/converters/calendars/gregorian/converter.py
index 30e2dfc..f51c0dc 100644
--- a/src/undate/converters/calendars/gregorian/converter.py
+++ b/src/undate/converters/calendars/gregorian/converter.py
@@ -100,7 +100,7 @@ def parse(self, value: str) -> Undate:
 
         # parse the input string, then transform to undate object
         try:
-            # parse the string with our Hebrew date parser
+            # parse the string with our Gregorian date parser
             parsetree = gregorian_parser.parse(value)
             # transform the parse tree into an undate object
             undate_obj = self.transformer.transform(parsetree)
diff --git a/src/undate/converters/grammars/gregorian_multilang.lark b/src/undate/converters/grammars/gregorian_multilang.lark
index a4d6045..5cd2927 100644
--- a/src/undate/converters/grammars/gregorian_multilang.lark
+++ b/src/undate/converters/grammars/gregorian_multilang.lark
@@ -1,15 +1,15 @@
 // WARNING: This file is auto-generated. DO NOT EDIT.
 // To regenerate: hatch run codegen:generate
 
-month_1: "January" | "Jan" | "enero" | "ene" | "janvier" | "janv" | "Januar" | "Mutarama" | "mut" | "Janwaliyo" | "ጥሪ"
-month_2: "February" | "Feb" | "febrero" | "feb" | "février" | "févr" | "Februar" | "Gashyantare" | "gas" | "Febwaliyo" | "ለካቲት" | "ለካ"
-month_3: "March" | "Mar" | "marzo" | "mar" | "mars" | "März" | "Werurwe" | "wer" | "Marisi" | "መጋቢት" | "መጋ"
-month_4: "April" | "Apr" | "abril" | "abr" | "avril" | "avr" | "Mata" | "mat" | "Apuli" | "Apu" | "ሚያዝያ" | "ሚያ"
-month_5: "May" | "mayo" | "may" | "mai" | "Mai" | "Gicurasi" | "gic" | "Maayi" | "Maa" | "ጉንበት" | "ግን"
-month_6: "June" | "Jun" | "junio" | "jun" | "juin" | "Juni" | "Kamena" | "kam" | "Juuni" | "Juu" | "ሰነ"
-month_7: "July" | "Jul" | "julio" | "jul" | "juillet" | "juil" | "Juli" | "Nyakanga" | "nya" | "Julaayi" | "ሓምለ" | "ሓም"
-month_8: "August" | "Aug" | "agosto" | "ago" | "août" | "Kanama" | "kan" | "Agusito" | "Agu" | "ነሓሰ" | "ነሓ"
-month_9: "September" | "Sep" | "septiembre" | "sept" | "septembre" | "Sept" | "Nzeri" | "nze" | "Sebuttemba" | "Seb" | "መስከረም" | "መስ"
-month_10: "October" | "Oct" | "octubre" | "oct" | "octobre" | "Oktober" | "Okt" | "Ukwakira" | "ukw" | "Okitobba" | "Oki" | "ጥቅምቲ" | "ጥቅ"
-month_11: "November" | "Nov" | "noviembre" | "nov" | "novembre" | "Ugushyingo" | "ugu" | "Novemba" | "ሕዳር" | "ሕዳ"
-month_12: "December" | "Dec" | "diciembre" | "dic" | "décembre" | "déc" | "Dezember" | "Dez" | "Ukuboza" | "uku" | "Desemba" | "Des" | "ታሕሳስ" | "ታሕ"
+month_1: /(janwaliyo|mutarama|january|janvier|januar|enero|janv|jan|ene|mut|ጥሪ)/i
+month_2: /(gashyantare|febwaliyo|february|febrero|février|februar|févr|ለካቲት|feb|gas|ለካ)/i
+month_3: /(werurwe|marisi|march|marzo|mars|märz|መጋቢት|mar|wer|መጋ)/i
+month_4: /(april|abril|avril|apuli|mata|ሚያዝያ|apr|abr|avr|mat|apu|ሚያ)/i
+month_5: /(gicurasi|maayi|mayo|ጉንበት|may|mai|gic|maa|ግን)/i
+month_6: /(kamena|junio|juuni|june|juin|juni|jun|kam|juu|ሰነ)/i
+month_7: /(nyakanga|juillet|julaayi|julio|july|juil|juli|jul|nya|ሓምለ|ሓም)/i
+month_8: /(agusito|august|agosto|kanama|août|aug|ago|kan|agu|ነሓሰ|ነሓ)/i
+month_9: /(septiembre|sebuttemba|september|septembre|nzeri|መስከረም|sept|sep|nze|seb|መስ)/i
+month_10: /(ukwakira|okitobba|october|octubre|octobre|oktober|ጥቅምቲ|oct|okt|ukw|oki|ጥቅ)/i
+month_11: /(ugushyingo|noviembre|november|novembre|novemba|nov|ugu|ሕዳር|ሕዳ)/i
+month_12: /(diciembre|december|décembre|dezember|ukuboza|desemba|ታሕሳስ|dec|dic|déc|dez|uku|des|ታሕ)/i
diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
index 6cb7ba6..3938bad 100644
--- a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_parser.py
@@ -38,6 +38,9 @@
     # French
     "18 avril 2025",
     "18 avr. 2025",
+    # case-insensitive
+    "18 JUNE 2025",
+    "Avril 2025",
 ]
 
 
@@ -51,7 +54,7 @@ def test_should_parse(date_string):
     ("0 June 1006", UnexpectedCharacters),
     ("42 March 1206", UnexpectedCharacters),
     # month alone
-    ("Juin", UnexpectedCharacters),
+    ("Juin", UnexpectedEOF),
     # day only
     ("12 ", UnexpectedEOF),
     # non-Gregorian month

From a29a5a4e338fbd66a9f27e71d00d669d7907a4a1 Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:21:09 -0500
Subject: [PATCH 13/17] Test error handling in gregorian converter parse method

---
 .../test_gregorian/test_gregorian_converter.py         | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
index f506d23..9839b34 100644
--- a/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
+++ b/tests/test_converters/test_calendars/test_gregorian/test_gregorian_converter.py
@@ -1,3 +1,6 @@
+import pytest
+
+
 from undate.date import DatePrecision
 from undate.undate import Undate, Calendar
 from undate.converters.calendars import GregorianDateConverter
@@ -65,3 +68,10 @@ def test_parse(self):
         assert date.calendar == Calendar.GREGORIAN
         assert date.precision == DatePrecision.YEAR
         assert date.label == date_str
+
+    def test_parse_errors(self):
+        with pytest.raises(ValueError, match="empty string is not supported"):
+            GregorianDateConverter().parse("")
+
+        with pytest.raises(ValueError, match="Could not parse"):
+            GregorianDateConverter().parse("Foo 1920")

From b9c2bf6d1eeda935203883b388ada7e3f838f29e Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:29:03 -0500
Subject: [PATCH 14/17] Catch more generic Lark exception per @coderabbitai

---
 src/undate/converters/calendars/gregorian/converter.py | 4 ++--
 src/undate/converters/calendars/hebrew/converter.py    | 4 ++--
 src/undate/converters/calendars/islamic/converter.py   | 4 ++--
 src/undate/converters/combined.py                      | 4 ++--
 src/undate/converters/edtf/converter.py                | 8 ++++----
 5 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/undate/converters/calendars/gregorian/converter.py b/src/undate/converters/calendars/gregorian/converter.py
index f51c0dc..9aa954d 100644
--- a/src/undate/converters/calendars/gregorian/converter.py
+++ b/src/undate/converters/calendars/gregorian/converter.py
@@ -1,6 +1,6 @@
 from calendar import monthrange, isleap
 
-from lark.exceptions import UnexpectedCharacters
+from lark.exceptions import UnexpectedInput
 
 from undate.undate import Undate
 from undate.converters.base import BaseCalendarConverter
@@ -107,5 +107,5 @@ def parse(self, value: str) -> Undate:
             # set the original date string as the label
             undate_obj.label = value
             return undate_obj
-        except UnexpectedCharacters as err:
+        except UnexpectedInput as err:
             raise ValueError(f"Could not parse '{value}' as a Gregorian date") from err
diff --git a/src/undate/converters/calendars/hebrew/converter.py b/src/undate/converters/calendars/hebrew/converter.py
index a8fdfe7..dc8ad19 100644
--- a/src/undate/converters/calendars/hebrew/converter.py
+++ b/src/undate/converters/calendars/hebrew/converter.py
@@ -1,7 +1,7 @@
 from typing import Union
 
 from convertdate import hebrew  # type: ignore
-from lark.exceptions import UnexpectedCharacters
+from lark.exceptions import UnexpectedInput
 
 from undate import Undate, UndateInterval
 from undate.converters.base import BaseCalendarConverter
@@ -111,7 +111,7 @@ def parse(self, value: str) -> Union[Undate, UndateInterval]:
             # set the original date as a label, with the calendar name
             undate_obj.label = f"{value} {self.calendar_name}"
             return undate_obj
-        except UnexpectedCharacters as err:
+        except UnexpectedInput as err:
             raise ValueError(f"Could not parse '{value}' as a Hebrew date") from err
 
     # do we need to support conversion the other direction?
diff --git a/src/undate/converters/calendars/islamic/converter.py b/src/undate/converters/calendars/islamic/converter.py
index 67f2a64..fae7f7f 100644
--- a/src/undate/converters/calendars/islamic/converter.py
+++ b/src/undate/converters/calendars/islamic/converter.py
@@ -1,7 +1,7 @@
 from typing import Union
 
 from convertdate import islamic  # type: ignore
-from lark.exceptions import UnexpectedCharacters
+from lark.exceptions import UnexpectedInput
 
 from undate import Undate, UndateInterval
 from undate.converters.base import BaseCalendarConverter
@@ -97,7 +97,7 @@ def parse(self, value: str) -> Union[Undate, UndateInterval]:
             # set the original date as a label, with the calendar name
             undate_obj.label = f"{value} {self.calendar_name}"
             return undate_obj
-        except UnexpectedCharacters as err:
+        except UnexpectedInput as err:
             raise ValueError(f"Could not parse '{value}' as an Islamic date") from err
 
     # do we need to support conversion the other direction?
diff --git a/src/undate/converters/combined.py b/src/undate/converters/combined.py
index c74beb9..ec08c31 100644
--- a/src/undate/converters/combined.py
+++ b/src/undate/converters/combined.py
@@ -7,7 +7,7 @@
 from typing import Union
 
 from lark import Lark
-from lark.exceptions import UnexpectedCharacters
+from lark.exceptions import UnexpectedInput
 from lark.visitors import Transformer, merge_transformers
 
 from undate import Undate, UndateInterval
@@ -77,7 +77,7 @@ def parse(self, value: str) -> Union[Undate, UndateInterval]:
             parsetree = parser.parse(value)
             # transform returns a list; we want the first item in the list
             return self.transformer.transform(parsetree)[0]
-        except UnexpectedCharacters:
+        except UnexpectedInput:
             raise ValueError(
                 "Parsing failed: '%s' is not in a recognized date format" % value
             )
diff --git a/src/undate/converters/edtf/converter.py b/src/undate/converters/edtf/converter.py
index d0b742f..e5eddac 100644
--- a/src/undate/converters/edtf/converter.py
+++ b/src/undate/converters/edtf/converter.py
@@ -1,6 +1,6 @@
 from typing import Optional, Union
 
-from lark.exceptions import UnexpectedCharacters
+from lark.exceptions import UnexpectedInput
 
 from undate import Undate, UndateInterval
 from undate.converters.base import BaseDateConverter
@@ -40,10 +40,10 @@ def parse(self, value: str) -> Union[Undate, UndateInterval]:
         try:
             parsetree = edtf_parser.parse(value)
             return self.transformer.transform(parsetree)
-        except UnexpectedCharacters:
+        except UnexpectedInput as err:
             raise ValueError(
-                "Parsing failed: '%s' is not a supported EDTF date format" % value
-            )
+                f"Parsing failed: '{value}' is not a supported EDTF date format"
+            ) from err
 
     def _convert_missing_digits(
         self, value: Optional[str], old_missing_digit: str

From bb1d724d01b803b0ad3e04d851e0ecc28240f71c Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:39:04 -0500
Subject: [PATCH 15/17] Ignore commas and periods across all grammars

---
 src/undate/converters/calendars/hebrew/parser.py  | 7 ++++---
 src/undate/converters/calendars/islamic/parser.py | 7 ++++---
 src/undate/converters/grammars/combined.lark      | 7 +++----
 src/undate/converters/grammars/gregorian.lark     | 7 +++----
 src/undate/converters/grammars/hebrew.lark        | 9 ++++++---
 src/undate/converters/grammars/islamic.lark       | 4 ++++
 6 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/src/undate/converters/calendars/hebrew/parser.py b/src/undate/converters/calendars/hebrew/parser.py
index 3056f85..074d2c5 100644
--- a/src/undate/converters/calendars/hebrew/parser.py
+++ b/src/undate/converters/calendars/hebrew/parser.py
@@ -4,6 +4,7 @@
 
 grammar_path = GRAMMAR_FILE_PATH / "hebrew.lark"
 
-with open(grammar_path) as grammar:
-    # NOTE: LALR parser is faster but can't be used to ambiguity between years and dates
-    hebrew_parser = Lark(grammar.read(), start="hebrew_date", strict=True)
+# open based on filename to allow relative imports based on grammar file
+hebrew_parser = Lark.open(
+    str(grammar_path), rel_to=__file__, start="hebrew_date", strict=True
+)
diff --git a/src/undate/converters/calendars/islamic/parser.py b/src/undate/converters/calendars/islamic/parser.py
index 61a0cf0..d753a7a 100644
--- a/src/undate/converters/calendars/islamic/parser.py
+++ b/src/undate/converters/calendars/islamic/parser.py
@@ -4,6 +4,7 @@
 
 grammar_path = GRAMMAR_FILE_PATH / "islamic.lark"
 
-with open(grammar_path) as grammar:
-    # NOTE: LALR parser is faster but can't be used due to ambiguity between years and days
-    islamic_parser = Lark(grammar.read(), start="islamic_date", strict=True)
+# open based on filename to allow relative imports based on grammar file
+islamic_parser = Lark.open(
+    str(grammar_path), rel_to=__file__, start="islamic_date", strict=True
+)
diff --git a/src/undate/converters/grammars/combined.lark b/src/undate/converters/grammars/combined.lark
index 1f87208..3f6a568 100644
--- a/src/undate/converters/grammars/combined.lark
+++ b/src/undate/converters/grammars/combined.lark
@@ -1,10 +1,9 @@
 %import common.WS
 %ignore WS
 
-// Some abbreviations use periods; some default date formats
-// include commas. Ignore both. (Copied from gregorian.lark)
-PUNCTUATION: "." | ","
-%ignore PUNCTUATION
+// Ignore periods and commas in dates
+%import .undate_common.DATE_PUNCTUATION
+%ignore DATE_PUNCTUATION
 
 start: (edtf__start | hebrew__hebrew_date  | islamic__islamic_date | gregorian__gregorian_date )
 
diff --git a/src/undate/converters/grammars/gregorian.lark b/src/undate/converters/grammars/gregorian.lark
index 74cff9b..93338f9 100644
--- a/src/undate/converters/grammars/gregorian.lark
+++ b/src/undate/converters/grammars/gregorian.lark
@@ -1,10 +1,9 @@
 %import common.WS
 %ignore WS
 
-// Some abbreviations use periods; some default date formats
-// include commas. Ignore both
-PUNCTUATION: "." | ","
-%ignore PUNCTUATION
+// Ignore periods and commas in dates
+%import .undate_common.DATE_PUNCTUATION
+%ignore DATE_PUNCTUATION
 
 %import .gregorian_multilang (month_1, month_2, month_3, month_4, month_5,  \
 	month_6, month_7, month_8, month_9, month_10, month_11, month_12)
diff --git a/src/undate/converters/grammars/hebrew.lark b/src/undate/converters/grammars/hebrew.lark
index 118ed98..1b28d19 100644
--- a/src/undate/converters/grammars/hebrew.lark
+++ b/src/undate/converters/grammars/hebrew.lark
@@ -1,9 +1,13 @@
 %import common.WS
 %ignore WS
 
+// Ignore periods and commas in dates
+%import .undate_common.DATE_PUNCTUATION
+%ignore DATE_PUNCTUATION
+
 // only support day month year format for now
 // parser requires numeric day and year to be distinguished based on order
-hebrew_date: weekday? day month comma? year | month year | year
+hebrew_date: weekday? day month year | month year | year
 
 // TODO: handle date ranges?
 
@@ -31,8 +35,7 @@ month: month_1
 // months have 29 or 30 days; we do not expect leading zeroes
 day: /[1-9]/ | /[12][0-9]/ | /30/
 
-comma: ","
-weekday: ("Monday" | "Tuesday" | "Wednesday" | "Thursday" | "Friday" | "Saturday" | "Sunday") comma?
+weekday: ("Monday" | "Tuesday" | "Wednesday" | "Thursday" | "Friday" | "Saturday" | "Sunday")
 
 
 // months, in order; from convertdate list
diff --git a/src/undate/converters/grammars/islamic.lark b/src/undate/converters/grammars/islamic.lark
index 1e4940b..530116a 100644
--- a/src/undate/converters/grammars/islamic.lark
+++ b/src/undate/converters/grammars/islamic.lark
@@ -1,6 +1,10 @@
 %import common.WS
 %ignore WS
 
+// Ignore periods and commas in dates
+%import .undate_common.DATE_PUNCTUATION
+%ignore DATE_PUNCTUATION
+
 // only support day month year format for now
 // parser requires numeric day and year to be distinguished based on order
 islamic_date: weekday? day month year | month year | year

From e16f4d26f9702c856c168a081ddaa25f2f931907 Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:40:03 -0500
Subject: [PATCH 16/17] Use markdown formatting instead of rst for hatch run
 command

---
 DEVELOPER_NOTES.md | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/DEVELOPER_NOTES.md b/DEVELOPER_NOTES.md
index e74c145..f77f330 100644
--- a/DEVELOPER_NOTES.md
+++ b/DEVELOPER_NOTES.md
@@ -97,10 +97,9 @@ The Gregorian Lark parser includes a script-generated file, which
 populates month names based on a list of language codes using the Babel
 library.  To regenerate, run the script with hatch (which should
 be installed globally)::
-
-    hatch run codegen:generate
+```sh
+hatch run codegen:generate
+```
     
 When the `.lark` file is modified by the script, it must be committed to git.
 
-
-

From 3efce6de651f31f6e9674413ca9f9e4d4528b61e Mon Sep 17 00:00:00 2001
From: rlskoeser <rebecca.s.koeser@princeton.edu>
Date: Thu, 12 Feb 2026 15:41:15 -0500
Subject: [PATCH 17/17] Add new undate_common lark grammar to version control

---
 src/undate/converters/grammars/undate_common.lark | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 src/undate/converters/grammars/undate_common.lark

diff --git a/src/undate/converters/grammars/undate_common.lark b/src/undate/converters/grammars/undate_common.lark
new file mode 100644
index 0000000..ac42b47
--- /dev/null
+++ b/src/undate/converters/grammars/undate_common.lark
@@ -0,0 +1,3 @@
+// Some abbreviations use periods; some default date formats
+// include commas. Ignore both
+DATE_PUNCTUATION: "." | ","