There a plenty of resources that can show you when are the best times to post to Facebook in general, but what’s really important is finding out when YOUR fans & likers are active on Facebook, so that you can choose the best times to post content.
Facebook has recently changed its algorithm with how it decides which posts users see, and which ones don’t. One thing that is now quite important is how old your post was. The older the post, the less likely it is to show up in your fans newsfeeds. The best way to get around this is by finding out when is the best time to post content, so that your posts are ‘new’.