bitcoin two identical R
Interesting find! 


  when it happen?


2012-03-09 19:20:14, according to blockchain.info.


  why it happen?


It seems that someone was using a faulty signing process. The R value will only be the same if the same k value is chosen during the ECDSA signing process. 


  how it Happen?


Hard to say, as the person who made that transaction is probably hard to find. It could have been done by faulty software, or it could have been done intentionally to see if anyone would recognize it and steal the coins (since using the same k value twice on different signatures leaks the private key).