When starting an approval with "Deadline at", the time zone offset is preselected for the default deadline date (now + the default period from settings). If the user then picks a date on the other side of a clock change, the
preselected offset no longer matches that date and the saved deadline is shifted by one hour.

Proposal: show a message next to the time zone select when the entered date has a different offset than the preselected one, so the user knows the time will shift and can pick the right offset.