Blue moon July 2015

There was a blue moon in July 2015. It doesn't mean the moon turned blue, it means there are 2 full moons in one month. The first occurred on 2 July and I had already blogged about it here. Then on 31st July there was another full moon.

This blue moon was the first one since 2012 and the next one will  be in 2018.

Blue moons are due to the difference between calendar and lunar months. A calendar month is 28 - 31 days, but a lunar month is always 29.53 days long, i.e. the time interval between 2 full moons.