CiviMail scheduling problem due to timezone issues
I've never changed the scheduled date directly in civicrm_mailing, but it seems like a pretty harmless maneuver.

If your CMS is WordPress, I have a fork of wp-cli here that lets you specify the time zone in which a cron job should assume it runs.  It's specifically to handle a WordPress/Civi multisite where different sites are maintained by users in different time zones.  Each site's cron job runs in that site's local time zone.