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.
All legacy (hg-git based) Projects have been automatically migrated to native with the upgrade of 2025-01-23
This MR proposes two main changes: