Also known as: にゃんにゃんにゃんの日, 2月22日, 猫の日, ネコの日, ねこの日, ねこのひ, 2月22日は猫の日
February 22, or 2.22
Read "Ni Ni Ni", then taken further into the day pun "nyan nyan nyan," artists have taken this and made February 22 into the day of catgirl Omake.
Not to be confused with International Cat Day, a worldwide celebration on August 8th.