It's March 21.
Can't wait for flying Pee-kachu.
I use an action replay for the events
It seems the Pichu event is over Wi-fi. You get the Pikachu-colored-Pichu over Wi-fi, and going to Celebi's shrine prompts an encounter with a spiky-eared Pichu. It's going on until March 25th.
Go to the SS/HG menu and do Mystery Gift -> From WIFI, see if you get anything. I'm installing the driver for my Nintendo Wi-Fi USB drive right now because my home Wi-fi doesn't like my DS.