lowzl wrote:

I think I've identified the problem. This affects everything in sprintfDate
which calculates using a UNIX timestamp. There are two possible ways to fix it.

First option: move the call to timeanddate() in Parser.php out of the scope
where TZ is altered:

if ( isset( $wgLocaltimezone ) ) {
$oldtz = getenv( 'TZ' );
putenv( 'TZ='.$wgLocaltimezone );
}
$timestamp = date( 'YmdHis' );
if ( isset( $wgLocaltimezone ) ) {
putenv( 'TZ='.$oldtz );
}
$d = $wgContLang->timeanddate( $timestamp , false, false) .

' (' . date( 'T' ) . ')';

Alternatively, change the calls to date() in Language.php to gmdate(). I'm not
sure which one is more correct, since it isn't stated anywhere whether
sprintfDate() takes UTC timestamp and formats it in accordance to the TZ
environment variable, or if it takes any timestamp and does no timezone adjustment.

Fixed, I hope, in r23017.

{{CURRENT*}} functions now consistently use UTC as intended, while
{{LOCAL*}} functions return local time per server config or $wgLocaltimezone.

Signature dates for Japanese and other languages including weekday now show
the correct day to match the rest of the time in local time.

Previously there was a weird mix, where {{CURRENT*}} sometimes used server local time while {{LOCAL*}} used $wgLocaltimezone, and sometimes either were just borked.