When is it Red Nose Day in 2012?

There isn't one ! Red-nose day is held every two years, so the next event will be next year (2013).

Here is an extract from Wikipedia's entry on the fund-raising event - "...The highlight of Comic Relief's appeal is Red Nose Day, a biennial telethon held in March..."

The term 'biennial' means an event occurring every two years. The event is usually in March.