>>487 そうでしたね。RFC2616の該当部分は、
RFC 2616
3.3 Date/Time Formats
3.3.1 Full Date
All HTTP date/time stamps MUST be represented in Greenwich Mean Time
(GMT), without exception. For the purposes of HTTP, GMT is exactly
equal to UTC (Coordinated Universal Time). This is indicated in the
first two formats by the inclusion of "GMT" as the three-letter
abbreviation for time zone, and MUST be assumed when reading the
asctime format.
ここになりますか。