The data conflicts. There are no easy answers. Knowing when to post to social media involves reflecting on the disagreeing data, paying attention to your own insights and analytics from Facebook and other sites, and then applying some common sense to what YOU know about YOUR social community.
I've made a calendar that gives you some of the DATA. But don't run your social posting life soley by this. These are national numbers. They don't reflect your time zone exactly, they may not reflect the particulars of the community you serve and nothing can replace real time experiences that convince you of good posting patterns. Direct LINK to the Calendar.
Part of being more "human" as a business in social media is NOT becoming clockwork predictable.