When match_digit() guesses a four-digit string to tell if it is
a year or a timezone, it did not consider that some real-world
places have UTC offsets equal to +1400.
$ date; TZ=UTC0 date; TZ=Pacific/Kiritimati date
Wed Jun 7 23:25:42 PDT 2006
Thu Jun 8 06:25:42 UTC 2006
Thu Jun 8 20:25:42 LINT 2006
Signed-off-by: Paul Eggert <eggert@CS.UCLA.EDU> Signed-off-by: Junio C Hamano <junkio@cox.net>