There is no fixed time to post on any social media platform.
The best time for posting on social media is not easy,
When you posting randomly there is possiblitly to have less reach and engagement. when your friends are not online they might miss your post. All you need to check your analytic data. To find what time most of your fans are online, and note that time to schedule post on the same time, so you have a huge chance of having more reach and engagement.
Follow the same method for all platform to gain followers and account reach.