The best time to post across industries is 9:00 AM when people are just starting work and going online for the first time.to get more traffic from social media especially facebook is on Tuesday and thursday
Check your instagram insight or facebook insight when are your users online post at that time. for me arround 10.4k followers are active at 9pm (all indian crowd)
morning when everyone's off to their work in public transport they're likely to check instagram so you can get better reach.
different type of audience are active at different time if you've a meme channel your target audience might me college students that the reason you're getting such result.