Due to bad planning on my part, 24 hours early.
To explain, I was out with some mates clubbing and partying, and left the club at 6.30AM of the day I had to go skirmishing, and started airsofting at 9.30. As I didn't sleep at all that day...
To make things more fun, it was a 2 day+1night event, for which I had 2 hours sleep.
Not something I intend on trying again.