Last year we had some big problems with times shifting, and today it happened again. We have an entry with a large matrix that has some 200 rows and each row has a start and end time. We had not had problems with this since November, but suddenly today upon saving this entry each time field shifted 1 minute back. So 2:00 PM became 1:59 PM etc.
It is a pain to change all the fields back manually each time this happens. Last time we had this it had something to do with DST and it was a whole hour. Updating to the new version of EE fixed it then. This particular site is still on 2.1.1 but we have not updated this installation as everything was working fine and we have a lot of problems with 2.1.3 on another site.
How can this suddenly happen without updating EE? Why would all the fields suddenly jump back a minute?
I found this thread from 2009 (!): http://ellislab.com/forums/viewthread/113395/ but no solution given. This seems to be an ongoing thing.