This is kind of an obscure question, but I'm curious.
Did the bitcoin developers mine blocks 0-513 in 2011 and then sit on them for over a year, or were they mined in 2012 and backdated for some reason?
For reference, as I learned from this answer, testnet3 was adopted by this commit. I'm a little confused as to the exact date;
git log appears to show it as 12 April 2012, while github gives 25 May 2012. (Maybe the discrepancy has to do with when the change was made in whose repo?) The first release with testnet3 was 0.7.0, released 17 September 2012.