You can find different data regarding to this. It can depend on the source you're reading, whether the niche is SFW or NSFW, just to mention something obvious.
You need to know your audience too. Are they adults working 9-5 jobs, stay at home moms/dads, college kids, night owls? You also need to know the location of your audience. In big countries with multiple time zones it's not enough to know the country, you'll need more precise data to be able to find out the top time zone(s).
And when you think you figured out the most busiest hours to post, you aren't done yet. There's another thing to consider: those are the hours when most of the posts occur, so you need to compete with a lot more posts than if you'd be posting in less busy hours. It's very similar when particular eBay sellers schedule their listings to end in night hours, because there's less competition, although there are also less buyers.
Different studies show that most of the posts occur between 15:00 and 16:00. What does this mean? That you should avoid posting in that time slot.
Most people sleep 7-8 hours a day (let's say from 00:00 to 07:00), that 1/3rd of the day is not a good time to post, the other 2/3rd is a go generally. Experiment. Start posting at 07:00 EST (04:00 PST) and stop at 00:00 EST (21:00 PST).
There seem to be a consensus on the best days to post and those are Wednesday and Thursday. I can't attest to this, but multiple studies came to this conclusion, so there must be some truth to it.
The best time to post can depend on the media type too. Most of the data what you can gather applies to picture posting (unless stated otherwise), but not video posting. It's different, videos should be posted in the evening hours or at night, because people like to watch those in full with sound at home (after work/school).
The best you can do is experiment with your audience and note engagement patterns.
