Reddit's default sort rewards posts that gain votes quickly. A post that collects twenty upvotes in its first hour outranks one that collects fifty over a day, because the ranking is a function of velocity and age rather than raw score. That single design decision is why timing carries more weight on Reddit than on a feed that will happily resurface a good post the next morning.
It also means a well-written post dropped into a sleeping subreddit is simply lost. Not downranked — never seen. There is no second chance for the same submission.
Read the subreddit, not a chart
The fastest way to find the window is to let the community show you. Open the subreddit, sort by Top with a filter of This Week, and look at the timestamps on the posts that made it. Do that across two or three weeks and the pattern is usually obvious within a dozen posts.
- Sort by Top → This Week, and note the posting hour of the top ten. You are looking for a cluster, not a single winner.
- Check the subreddit's own timezone gravity. A UK-heavy community peaks hours before a US-heavy one, and subscriber count tells you nothing about where those subscribers are.
- Weekends are not universally worse. Hobby and consumer subreddits often peak on Saturday morning; professional ones usually do not.
- Avoid the first hour of the biggest daily thread, if the subreddit has one — you are competing with it for the same attention.
Timing will not rescue a post the subreddit did not want
It is worth saying plainly, because timing is the easiest variable to obsess over and the least likely to be your actual problem. If a post is removed by automod for a karma or account-age rule, the hour is irrelevant. If it reads as promotion in a community that does not allow it, the hour is irrelevant. If it answers a question nobody in that subreddit was asking, the hour is irrelevant.
Get the subreddit fit right first. Timing is a multiplier on a post that was going to work anyway, and a rounding error on one that was not.