The best time to post is the window when your audience is online and most receptive, so a post gets early engagement that the ranking system can build on. Generic "best time" charts are only a starting point; the real answer is specific to your account, your audience's time zones and habits, and the platform.
It matters because timing shapes the crucial first minutes. Modern feeds are not strictly chronological, but early interaction still signals a post is worth wider distribution, so publishing into an active audience can lift reach on the same creative.
Find yours from your own analytics — when your followers are active and when your past posts performed — then test around those windows rather than trusting a global average. Consistency matters more than perfection: a reliable schedule your audience learns to expect beats chasing the "perfect" minute.