BuddyPress.org

@DJPaul
I finally found the reason.
It is due to my customization of the plugin named “BuddyPress Group Email Subscription”.
Due to the setting of WP3.0.1, which forces Time zone to UTC ignoring the local date_default_timezone_set, the plugin claims that the server time is UTC. As a result, the displayed time from the plugin is 9 hours behind Japan time.

For this reason, I added “date_default_timezone_set(‘Asia/Tokyo’);” to the plugin’s script, which is the reason of the problem I posted here.

Ummm….
I should once again think about the solution how to fix the plugin. Any idea?