provcat.timestamps

?at=ts:TIME picks the version that a branch had at TIME. TIME is one of:

• a date, 2026-10-01, which means 00:00 UTC that day;
• a date and time, 2026-10-01T12:30:00, with an optional zone such as Z or +05:30; a time without a zone is UTC;
• Unix seconds, 1793200661.

Write a + in a zone as %2B in a URI, because a URI can turn + into a space on the way.