Bored at work, found this:
4.7.2 Time Zones
To have the board time show correctly, please select your time zone. The
time in phpBB 2.0.0 does not work with Daylight Savings Time, so if you
have Daylight Savings Time, add 1 to your GMT modifier. So if you are
in GMT-5 and have DST, you will need to set your time zone to GMT-4.
Dunno if 2.0.4 does work, couldn't find the documentation for it.