States the run timestamp in UTC, whatever zone it ran in

All 4 scenarios hold

A report states the timestamp in UTC, whatever zone the build ran in. A report generated in CI then reads the same for every reader. The label a reader sees drops the sub-second precision nobody needs. The attribute beside it holds whole seconds, so a tool can compare the report against the revision it came from.

A report reads the clock unless the build pins an instant. A build that pins one gets the same bytes from the same tests, which is what a build comparing two runs needs. The rows below read reports the build pinned.