Blue Moon

I was told there was a blue moon tonight and as there won't be another until 2015 I thought I'd better blip it. There seems differing opinions about whether it is tonight or tomorrow but there is only 7 minutes of today left and I believed the Met Office, but I now think they were wrong.

A normal year has 12 full moons but every few years an extra one occurs due to the difference in days in calendar months and lunar months. One month then has two full moons, the second of which is the blue moon.