To easily change timezone on Ubuntu, run Terminal or connect to your remote Ubuntu over SSH and run:
$ sudo dpkg-reconfigure tzdata
And then you’re going to get screen in which you can set the geography area for you timezone.
Select your geographic area, in this example Europe, and press Enter.
Next you will get a shorter list of timezones, now you should select the city corresponding to your time zone, select it and press Enter.
And you’re finished. Now you can be sure that the time on your Ubuntu is the one you wanted.