I just discovered something interesting. If I hit reply to a toot, it's the time at which I do that that counts as the time I made the toot, and not when the toot actually sends (when I hit the TOOT button).
@NinahMarie I have no idea! Just noticed it when replying to someone: started to reply, tabbed out, tabbed back in, someone else had replied, I finished mine and posted and mine showed that it had posted a fewins before the last reply