how can i set time and date of all users
via sql
thanks
You mean set them all to a certain timezone??
AdminCP > Configuration and Settings > Settings > Date and Time Formats > Default Timezone Offset > and set the default time zone for all members and guests
A lot of user-based settings in the ACP don't affect currently registered users, however I think the time zone is different and does affect current users, so I think what ghazal said will work... if it doesn't, though, run this query in phpMyAdmin;
UPDATE `mybb_users` SET `timezone` = 'X';
X is the timezone offset, for example 4 for GMT+4, -7 for GMT-7, etc etc.