What is the best time to post?

Maybe in the morning. When I wake up, I tend to check Girls with Muscle like reading the newspaper. The better bet might be noon. People may check during lunch breaks, seeing what's new, favorite things for later.

I don't know the answer to this but if you're going to specify a time, it's pretty meaningless unless you also include a time zone.

I'm betting that 1700-1800 UTC is the busiest time.

I try to post when the Site stats say that there are 0 Waitlisted images. This way, the chances are higher that your pic will stay on top of the home page for a longer time.

The busiest time for site traffic is about 2100 UTC, but I don't know if this is actual visitors or stuff like search engine bots.

Every second of every minute of every hour in every day is a good time to post!

Good posts will get noticed at any time. Marginal posts rarely have a good time.