How does Tumblr determine the order of posts with the same post date outside the dashboard?

Question

On the dashboard, Tumblr posts appear in the order in which they were created (regardless of the date attached to them). But on the front-end (e.g. at mysite.tumblr.com), I'm seeing inconsistent order for posts with the same post date and time.

On a test Tumblr, I created the following posts in this order (post IDs in parens):

• Post A, dated 2013-08-14 7:00:00 (58279080752)
• Post B, dated 2013-08-14 7:00:00 (58279382194)
• Post C, dated 2013-08-15 7:00:00 (58314687302)
• Post D, dated 2013-08-15 7:00:00 (58314687868)

On my dashboard, they appear in proper reverse-chronological order of creation (assuming the IDs are sequential), D->C->B->A, but when I view my theme, they're in the order D->C->A->B.

So it seems that yesterday's posts are in reverse order of creation/ID, but today's posts are in the natural order of creation/ID. What would explain this inconsistency?

Note: I'm not interested in changing the order (I know I can just change the post date/time to do that). I'm interested in understanding the criteria Tumblr uses to order posts when they have the same date and time, which I cannot find documented.

Update: Here is an actual Tumblr I've created which displays this behavior: http://postordertest.tumblr.com/

Dentilingual

Probably your themes use a grid-layout.. just a thought. – Repairer

Good thought, but not in the case. It's a brand new Tumblr with the "Default" theme, which doesn't use a grid: tumblr.com/theme/36037 – Dentilingual

Answer 1

Unfortunately, I believe the answer to my own question is "no particular order".

I created another test Tumblr, this time with three posts per identical datetime. For August 15 7am, the posts are displayed in 3rd-1st-2nd order of ID. But for August 14 7am, posts appear in 1st-3rd-2nd order of ID. No apparent pattern or consistency.

Then, I created two more posts dated August 15 7am. After publishing post G, Tumblr displayed the posts in 4th-3rd-1st-2nd order of ID. Again, no apparent order, other than the fact that the newest post appeared first. But here's where things got strange. After publishing a final Post H (same date/time), the entire order of posts for that datetime changed: from 4th-3rd-1st-2nd to 1st-5th-2nd-3rd-4th.

At this point, I can only conclude that Tumblr displays posts on blogs with the same date/time in no particular (or even consistently arbitrary) order.

Dentilingual

Answer 2

Tumblr determines the order of posts by Tumblr Post IDs in descending order.

Teillo

This appears not to be the case. I've just added a link to a test Tumblr: the posts for day one (D & C) appear in descending order, but the posts for day two (A & B) appear in ascending order of Post ID. All times are 7:00am. – Dentilingual