如何在PHP/MySQL中增加4小时的时间

I'm working on a blog migration from a custom built blog to Wordpress. One of the fields that Wordpress is looking for in the database is a date/time stamp set to GMT, which is 4 hours ahead of our time. So I basically need to take our date/time stamp (in YYYY-MM-DD HH:MM:SS format), and add four hours to it. I was looking at the MySQL command "ADDTIME", but I think that only works on selects, not on inserts. I'm working on a blog migration from a custom b