I'm having this problem too. When I log out, the time is correct. When I go to time and date settings, the time is correct. But on the panel, the time is incorrect and doesn't change.
EDIT- I got mine fixed by changing to a standard date format and de-selecting the box for using network time. Don't know if both are necessary(just the de-selection of network time didn't fix it), or if that's even the right way to fix the problem, but it worked for me(using cinnamon 1.3).
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