time conversions over midnight

GTFS datetimes with hours >= 24 are not strictly valid datetimes. They're more like a date plus an interval value - this is the approach I use when I load GTFS data into databases. I'd consider separating the date part from the time part of the arrival/departure times, and then parsing the time part into a "seconds from midnight" value.

Thanks the suggestions. I did a combination of these two approaches. The times are already split because they are a general trip record for any date. I used a test filter to split into three types: today, span_midnight, tomorrow. Today was left alone, tomorrow were split, 24 subtracted from the hour part and then the h,m,s reassembled into a string. Span_midnight were parsed like tomorrow and a dummy date added to each one, one day apart. Then the new time interval arithmetic gave me the duration in minutes. Since it is only the 'night buses' that are a problem there were only 700 out of the million so the extra processing was trivial.