RFD for timestamp update and documentation

[ccoffin]

This RFD covers updates to the schema regarding the timestamp regex and timezone offset validation, as well as needed timestamp documentation updates.

Rendered RFD

[ccoffin]

Discussed in the 2/12/2026 QWG meeting:
Multiple QWG participants believe that we should leave schema validation as is for timestamps. Multiple participants do not think we should enforce more strict offset validation within the schema to match what CVE Services will be implementing. One participant did feel that we should enforce offset validation within the schema, so we may want to revisit again in the near future. The one piece we should keep in this RFD is to update the documentation to remove reference to ISO 8601 and GMT from the schema description. The RFD will be modified to reflect these discussions and changes.