datetime bug fixes
This MR proposes two main changes:
- Only return time-only for a single-day time interval, not two consecutive days.
- Stop using the '1900 backward compatibility date-base system' when (de)serializing dates before March 1900.
This instance will be upgraded to Heptapod 1.5.0rc2 (GitLab 16.11.1) on 2024-05-10 at 18:00 UTC+2
This MR proposes two main changes: