After first being displayed, the date/time shown in the active build jumps back an hour after a few seconds.  Refreshing the browser repeats the issue.

This may be related to having a time-zone set.  This configuration was set to "Europe/London", so the time is shown in BST.

The other build times are not affected, and the time is correct after job completion (or on the job page, if the link is followed).

The video clip is focussed on the active build and starts with the date/time after it had jumped.  Then the browser is refreshed, and the correct date/time is shown (27-May-2021 16:19 BST).  A few seconds later it jumps back (27-May-2021 15:19 BST).