Storing and Presenting DateTimes

• Always, always, always store datetimes in UTC
• this makes your life easier
• For presentation, use the viewer's local time zone

my $dt = get_datetime_from_database();

$dt->set_time_zone( $user->time_zone );

print $dt->datetime;

• Makes it easy to do calculations on your stored datetimes
• do appointments overlap?
• how long is a meeting?
• how many days vacation?