When should I post?
Enter the subreddit you want to post to here to see a graph of when the most popular posts were posted.
Top Posts by Day (your local time)
Top Posts by Hour of Day (your local time)
The magic API gremlins find all the posts during the current month (because that's how it works), pick the top 500 sorted by upvotes, and assemble a pretty histogram for you.
Yes, this means a smaller sample size near the beginning of the month.