If (Note that that's a big "if"), in fact, the issue is one of timezones, possible fixes range from a simple minded, hard-coded addition (or subtraction, as the case may be) to or from your localtime... to converting all your date and time functions to use GMT.

But "could be the issue" is a really poor foundation upon which to build a fix. First, determine if that "issue" is, indeed, the problem.