Check timezone handling in both frontend & backend

I have the feeling that we currently have a little timezone handling problem:

I added a configuration that started on 2010-01-01 in the sms frontend (that's the way I inserted it). However, when I load it from the database, I see a start date of 2009-12-31.

I guess the datepicker used a date like 2010-01-01 00:00:00; and because of a mismatch in timezones we lost one hour (2009-12-31 23:00:00). And when we format it, we get 2009-12-31.

It is part of this issue to check how the time handling works.