Great tool jga! You should put in a link to the github page for it in the post. I suggest you make an average/median best time to post based on all the days in the week. It is easier to keep in mind. I'd also put the follower section first, as it is by far the most interesting.

I also suggest you make it clear which timezone is used (or put in a notice that local time, i.e. the time of the computer of the web browser is used), even though it is local time, or else many users will always have some doubt/wonder.