The best way to really understand your audience and how your videos are really doing is via the YouTube analytics tab.
The analytics tab can tell you the time most of your subscribers are online. This will help you know when to post your videos. If your analytics say your audience are mostly online at 2pm, I’ll advise you post your video at 12pm or 1pm.
Reason is, by the time most of your subs are online, your video would have gained some traction so their engagement will just push it up further.
If you’re starting out, you won’t have access to such analytics because there won’t be enough data for YouTube to use. So you can post at any time you want or try different posting times to determine which works best for you.