We stumble on what seems to be a bug with daylight savings time not being picked up and, hence, showing the wrong (current) time for the user. We experienced this last year but at the time I dismissed it as some temporary glitch, but it happened again so it seems to be a seasonal bug. 
So, we use the option to display the user’s current time on their User Card:
All works well, until a change on daylight savings time comes around.
The particular case that I found was someone in the Netherlands (Europe/Amsterdam timezone, correctly set in the account) showing as being one hour ahead than it should. Netherlands changed their clocks on 26 March, which is likely why this popped up now. It seems to happen also for users in other timezones too: checked with Europe/Berlin (also CET/CEST) and also Europe/Helsinki (EET/EEST). My own timezone is Europe/Lisbon, but as far as I can tell, the wrong time shows incorrectly both for the user themselves and others in different timezones.
Restarting the instance did not fix it. However, rebuilding did fix it! So something seems to be specific to the time when the image is built that prevents daylight savings time changes from being reflected when they come by. Daylight savings time changes happen in different dates for different places, so scheduling rebuilds as a workaround is not very practical.
I have tested the fix (rebuilding) only on our staging/test instance so I still have our production instance having this issue in case someone wants to take a look (please send PM and I’ll share the details) since it will only be reproducible on an instance that hasn’t been rebuilt recently which can make it a bit tricky to debug/reproduce.