Blue Moon - The Blue Moon of 2009 and 2010

Our Blue Moon Calculator says that in 2009, there is a Blue Moon in December. You may have heard or read reports which said that the Blue Moon really occurs in January 2010 or March 2010. Who is right?

Well, you can see Blue Moons in December 2009 or January 2010 or March 2010, but it depends where in the world you live.

Let's start with the basic astronomical facts. The Full Moons from December 2010 to March 2010 are as follows:

2 December 2009	at	07:30 GMT
31 December 2009	at	19:13 GMT
30 January 2010	at	06:17 GMT
28 February 2010	at	16:38 GMT
30 March 2010	at	02:25 GMT

These dates and times have been calculated rigorously using the same methods as those employed by the United States Naval Observatory and by Her Majesty's Nautical Almanac Office. They are given in Greenwich Mean Time which is the standard time zone used by astronomers worldwide.

Here are those four Full Moons again, but with the dates and times adjusted for several major time zones around the world. For each time zone, the two Full Moons which fall in the same calendar month are highlighted.

City	Time zone	Full Moon 1	Full Moon 2	Full Moon 3	Full Moon 4	Full Moon 5
Places East of Greenwich
Auckland¹	GMT + 13 hours	December 2 20:30	January 1 08:13	January 30 19:17	March 1 05:38	March 30 15:25
Sydney¹	GMT + 11 hours	December 2 18:30	January 1 06:13	January 30 17:17	March 1 03:38	March 30 13:25
Tokyo	GMT + 9 hours	December 2 16:30	January 1 04:13	January 30 15:17	March 1 01:38	March 30 11:25
Beijing Perth	GMT + 8 hours	December 2 15:30	January 1 03:13	January 30 14:17	March 1 00:38	March 30 10:25
Ho Chi Minh (Saigon)	GMT + 7 hours	December 2 14:30	January 1 02:13	January 30 13:17	February 28 23:38	March 30 09:25
Mumbai	GMT + 5 hours 30 minutes	December 2 13:00	January 1 00:43	January 30 11:47	February 28 22:08	March 30 07:55
Islamabad	GMT + 5 hours	December 2 12:30	January 1 00:13	January 30 11:17	February 28 21:38	March 30 07:25
Moscow	GMT + 3 hours	December 2 10:30	December 31 22:13	January 30 09:17	February 28 19:38	March 30 05:25
Johannesburg	GMT + 2 hours	December 2 09:30	December 31 21:13	January 30 08:17	February 28 18:38	March 30 06:25
Paris	GMT + 1 hour	December 2 08:30	December 31 20:13	January 30 07:17	February 28 17:38	March 30 05:25
The Greenwich Meridian
London	GMT	December 2 07:30	December 31 19:13	January 30 06:17	February 28 16:38	March 30 02:25
Places West of Greenwich
Rio de Janeiro¹	GMT - 2 hours	December 2 05:30	December 31 17:13	January 30 04:17	February 28 14:38	March 30 00:25
New York Toronto	GMT - 5 hours	December 2 02:30	December 31 14:13	January 30 01:17	February 28 11:38	March 29 21:25
Chicago Mexico City	GMT - 6 hours	December 2 01:30	December 31 13:13	January 30 00:17	February 28 10:38	March 29 20:25
Calgary Tucson	GMT - 7 hours	December 2 00:30	December 31 12:13	January 29 23:17	February 28 09:38	March 29 19:25
Los Angeles Vancouver	GMT - 8 hours	December 1 23:30	December 31 11:13	January 29 22:17	February 28 08:38	March 29 18:25
Hawaii	GMT - 10 hours	December 1 21:30	December 31 09:13	January 29 20:17	February 28 06:38	March 29 16:25
¹ These places observe daylight saving time.

As you can see, Europe, Africa, the Americas and Asia west of India have a Blue Moon in December 2009, whilst central Asia has a Blue Moon in January 2010.

The big surprise is that the Far East, Australia and New Zealand enjoy a rare double Blue Moon in 2010, when both January and March have two Full Moons. These regions of the world missed out on the double Blue Moon back in 1999 because the second Full Moon of that year was on 1 February for time zones more than seven hours ahead of GMT, so it's only fair that they get one in 2010 instead!

Acknowledgements

We thank Australian reader Jim Cahill for alerting us to the fact that the citizens of Western Australia voted not to switch to daylight saving time in 2009, so Perth is in the same time zone as Beijing, not Tokyo. Happily, they still get a double Blue Moon in 2010!

Once in a Blue Moon

The Blue Moons of 2009 and 2010

Acknowledgements