Question about Mao!

[eggy-egg.livejournal.com]

Does anyone know when Mao's birthday is?

My friend and I came across three fanart on Pixiv (here, here, and here) and they're all happy birthday pictures, all posted on January 1  (he really does suit being a Capricorn), and all by different artists. I'm just wondering where they got this information that his birthday is on January the first. I was always under the impression that we never find out his birth date, so is there supplementary media that supports him being born on January 1?

Update: Okay, two of the artists replied back to me and one of them said that his birthday was published in the September 2008 Animedia. So if anyone has that issue of Animedia, I guess they can check for proof...

It's also here. 

皇暦2000/1/1

マオ

So Mao is older than Lelouch!

Update 2: The third artist got back to me and said that this info could be found from the CRITICAL ZERO book.