The data I used were the submission score and creation time. I targeted mid-popularity subreddits to make sure there were enough data to draw conclusions and that it wouldn't take forever to gather the data, and settled on:

My hypothesis going in was that 6 - 9 pm central time would be best for these as that's when people in the US would be getting home from work and be most engaged on reddit. Throughout, I am using central time for all times since I live in Texas and I'm less likely to screw it up if I just use my timezone.

I considered all posts between December 17, 2016 and December 16, 2017. It's notable that highqualitygifs has significantly higher post scores overall.

'Did your post do well?' isn't really defined, so I used three different metrics:

did it do better than the median for the subreddit?

did it get a really high score (1000 for highqualitygifs/100 for the others)?

did it get ignored or rejected (score below 5)?

I broke it up by time of day and day of the week.





Results

Science had 8388 posts in this period. The metrics described above are plotted below:









The time of day range was 162 posts (3 AM) to 813 posts (9 AM). The day of the week range was 793 posts (Sunday) to 2007 posts (Thursday). The median score for posts in this subreddit was 31.





Dataisbeautiful had 9159 posts in this period. The metrics described above are plotted below:



The time of day range was 193 (2 AM) to 654 (9 AM). The day of the week range was 878 (Saturday) to 1902 (Thursday). The median score for posts in this subreddit was 12.





Changemyview had 7490 posts in this period. The metrics described above are plotted below:



The time of day range was 112 (5 AM) to 493 (2 PM). The day of the week range was 806 (Friday) to 1191 (Tuesday). The median score for posts in this subreddit was 9.





Highqualitygifs had 6943 posts in this period. The metrics described above are plotted below:













The time of day range was 116 (3 AM) to 718 (6 AM). The day of the week range was 792 (Saturday) to 1191 (Friday). The median score for posts in this subreddit was 83.





Conclusions

All four of the subreddits show a clear trend of posts doing best in the 3-5 hour window centered at 7 AM and doing worst around midnight. Around 7 AM, posts are more likely to beat the median post, more likely to break into the high score category, and less likely to be ignored. Interestingly, the day of the post only seems to matter for two of the subreddits (dataisbeautfiul and science). I don't have a great idea as to why that's the case.









If you're interested in doing this yourself, here's an example of the code used to mine the subreddits:



Sample Python Code





Anyway...it looks like my hypothesis might be wrong...based on the >30k posts analyzed across 4 subreddits here, posting near 7 am is your best bet for having it do well.If you're interested in doing this yourself, here's an example of the code used to mine the subreddits:













