Format 0 is the standard C-language format (without the trailing newline character). Format 1 includes the time zone abbreviation. Formats 0 and 1 use abbreviations for the day of the week and the month. Formats 2 and 3 avoid language dependent names (except for the time-zone code).
All fields are fixed length, except possibly the time zone abbreviation. The conversion process produces no more than 29 characters plus the terminating null character. This length allows for at least a 4 character representation of the time zone abbreviation.
Format Example time zone length 0 Sun Sep 16 01:03:52 1973 local time 24 + null 1 Sun Sep 16 01:03:52 EST 1973 local time 28* + null 2 1994-01-23 09:59:53 EST local time 23* + null 3 1994-01-23 14:59:53 UTC GMT 23 + null (*) the time zone length can vary