I like an infographic that actually tells us something useful. So, following the 'social media image sizing' one from a few weeks back, here's a 'when to post' infographic from QuickSprout.
I didn't used to think social media timings were important, but increasingly I think it is worth trying to hit times of peak engagement IF you're tweeting or posting something important, particularly when using social media as an organisation rather than just for yourself. If you've put effort into creating useful content, you want as many people to see it as possible.
Image courtesy of QuickSprout - click on it to view it on their site