It varies depending on your audience—I don’t think any kind of general advice will be helpful here. I’m not sure what platform you use but you should take a look at your follower insights to see what your most active posting times are (Instagram does this, not sure about other platforms)
You are already asking the wrong question. The proper question is:
“What is the best time to post an X kind of SM post on platform Y in order to reach my target audience of Z.”
Until you can state the kind of–for lack of better phrase–kind of engagement you are offering, on which specific platform, and which particular market demographic(s), there is no valid way to answer your question.
And, if you want to do it right, you will use different hooks to reel in different market segments in different SM areas.
I mean, you wouldn’t use fly fishing gear and lures to catch tuna off of Alaska, would you?