I was playing around with the Data Explorer and found to my surprise that several posts have received votes before they were created:
67 posts on Stack Overflow have received up-votes, down-votes, and/or favorites before their creation date. About a third of these were just within a week before its creation, but most were several months before with the most extreme having three favorite counts dated 1328 days before its creation date.
7 posts on Math exhibit being favorited before their creation date.
73 posts on Ask Ubuntu have been favorited before their creation date.
For all the sites I have tried running this query, I find posts like these. Curiously, only on Stack Overflow, a lot of posts have been up-voted and down-voted "before time" besides being favorited.
Why do votes cast before the creation date of the post exist? Is it because of migration? If then, shouldn't the creation date be migrated properly as the vote cast dates are? Or is this a bug?