The timezone data file used by boost::local_time::tz_database is described here: http://www.boost.org/doc/libs/1_39_0/doc/html/date_time/local_time.html#tz_d... My question is: Should the DST start time be specified in local time with or without DST applied? What about the DST end time? For example, America/New_York's start time is 2:00 AM. Is that 2:00 AM EST, or EDT? The end time is similar. The documentation says that the start time and end time is the "number of hours past midnight"; so I'm assuming that the start time is in non-DST, and the end time is in DST, but I just want to make sure. Thanks, Jason