When updating the timestamp of a topic via the UI, using up/down arrow keys to adjust time changes both time and date simultaneously.
It would be great if only the value in the current active field (be it date or time segment) is updated.
Using Firefox 85.0.2 on macOS 10.15.7.
Yes, this is feedback for @joffreyjaffeux – plus, I think there is an emerging browser standard for a native control here? Or am I mistaken? 
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/date
That’s just date, not time, of course.
sadly safari doesn’t actually support this ATM. However, support is present in technological preview so we should be able to remove all of this code at some point.
Safari technological preview:
I can have a look at the bug.
