Hi Ben;
It's a shame that the values aren't stored as a UNIX timestamp, as this would make things much easier.
Try splitting the H,M and S into an array by doing the following:
$time_array = split(":", $time);
where $time is the value from the database.
Then use:
$new_time = date("H:i", mktime($time_array[0],$time_array[1],$time_array[2]));
This will give $new_time the format of say: 20:07 for the time...
Cheers,
-D.