This timestamp is for the end of September, not August. Remember that a month value passed into timelocal is zero based (i.e. month 8 is Sept).

Perhaps this is not the problem you are seeing, but I would caution you from using the '1,1,1' value for the time, if you are just trying to generate a "date stamp". During daylight savings time in the US, in the spring time this may be an invalid time since the clock can jump an hour between midnight and 2 (or is it 3?) am, depending on your timezone. On Apr 3 of 2005 for example there is no such thing as 02:30 in my timezone since one second it was 01:59:59 and the next it was 03:00:00. Correspondingly there will be two different timestamps with the "same" time, in the fall. If you really want to calculate a date stamp, I'd suggest you use a time value that is known to be unique for the day (e.g. noon).