If you have LMDE installed alongside other distros on the same computer and the timezone is off on either install, this may be caused by LMDE setting your computer's internal clock to UTC. This fix tells LMDE to set your computer's internal clock to your local time. Some other distros set your computer's internal clock to your local time by default causing the time discrepancy. Try this fix below for LMDE:

Go Alt+F2 and type "gksu nautilus". Enter your password.

Once Nautilus is open, go to and open "/etc/default/rcS".

In the file, go to the "UTC=yes" section and correct it to "UTC=no".