How can a User's CreationDate be after they have posted?

Question

I am currently analysing an Archive-Datadump of the apple.stackexchange.org. When looking on the posts.xml together with the users.xml, there is a strange anomaly.

The earliest CreationDate among users.xml is in August 2010. The earliest post in the posts.xml is in 2008.

The profile of the user having posted the very first post in 2008 was only created in 2011. There several more cases in which the post's CreationDate is more than 100 days earlier than the user's CreationDate. Even for posts in recent years.

I assumed the user's CreationDate is the datetime of signup and signup is required for any postings.

Is there any explanation for this? Has there been a major change in user/profile/data architecture in August 2010?

Answer 1

There are two viable explanations that I know of:

1. Long ago, we sometimes allowed merges of profiles going from an older profile into a newer profile. The merge process always keeps the CreationDate of the destination profile, which meant any contributions they had on the older profile would have dates before then. We no longer allow this. Merges have to go into the older account now, which should make new situations of this technically impossible. (Note: There is no way for an ordinary user to confirm this situation because merge histories are not public.)

2. Migrations can cause weirdness. For the first item in your post, the question was originally posted on Stack Overflow and migrated to Apple after that site was created. The user did not have a profile on Apple at the time it was written, and the dates are both correct.