Order posts by two values

• planktonwebdesign

• September 15, 2014 at 2:32 pm

I want to do a wp_query and order the output based on a date that is used in the following custom fields.

start_date or festival_date

some of the posts have a start_date and some have a festival_date. I want to grab all the posts and order them by theses dates. I know how to order by start_date OR festival_date but not both.

Any help would be awesome!

Mike