There is one snag you're bound to run into -- Daylight Saving Time... Dealing with the times that straddle the transition from Standard Time into Daylight Time is somewhat easier than those straddling the opposite transition -- mainly because the latter involves an ambiguity (unless you also have a flag that indicates if the timestamp represents Standard or Daylight time). Fortunately, for the most part you have only one pair of transitions to deal with. This is part of the reason why I prefer timestamps kept in Universal Time rather than local time...