Server Setting
LocalSettings.php
$wgLocaltimezone = "Asia/Tokyo";
date_default_timezone_set( $wgLocaltimezone );
PHP Setting
date.timezone = Asia/Tokyo
Wiki
Server Setting
LocalSettings.php
$wgLocaltimezone = "Asia/Tokyo";
date_default_timezone_set( $wgLocaltimezone );
PHP Setting
date.timezone = Asia/Tokyo
Wiki
You can't change how server time is expressed in preferences, it will always be expressed in UTC. You can change the default timezone of the wiki for your users and unregistered users with $wgLocalTZoffset that will be used in page history, recent changes, etc, but not for signatures.