The Blue Moons 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 could see Blue Moons in December 2009 or in 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 2009 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 (GMT) which is the standard time zone used by astronomers worldwide.

Here are those 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	Dec 2 20:30	Jan 1 08:13	Jan 30 19:17	Mar 1 05:38	Mar 30 15:25
Sydney¹	GMT + 11 hours	Dec 2 18:30	Jan 1 06:13	Jan 30 17:17	Mar 1 03:38	Mar 30 13:25
Tokyo	GMT + 9 hours	Dec 2 16:30	Jan 1 04:13	Jan 30 15:17	Mar 1 01:38	Mar 30 11:25
Beijing Perth	GMT + 8 hours	Dec 2 15:30	Jan 1 03:13	Jan 30 14:17	Mar 1 00:38	Mar 30 10:25
Ho Chi Minh (Saigon)	GMT + 7 hours	Dec 2 14:30	Jan 1 02:13	Jan 30 13:17	Feb 28 23:38	Mar 30 09:25
Mumbai	GMT + 5 hours 30 minutes	Dec 2 13:00	Jan 1 00:43	Jan 30 11:47	Feb 28 22:08	Mar 30 07:55
Islamabad	GMT + 5 hours	Dec 2 12:30	Jan 1 00:13	Jan 30 11:17	Feb 28 21:38	Mar 30 07:25
Moscow	GMT + 3 hours	Dec 2 10:30	Dec 31 22:13	Jan 30 09:17	Feb 28 19:38	Mar 30 05:25
Johannesburg	GMT + 2 hours	Dec 2 09:30	Dec 31 21:13	Jan 30 08:17	Feb 28 18:38	Mar 30 06:25
Paris	GMT + 1 hour	Dec 2 08:30	Dec 31 20:13	Jan 30 07:17	Feb 28 17:38	Mar 30 05:25
The Greenwich Meridian
London	GMT	Dec 2 07:30	Dec 31 19:13	Jan 30 06:17	Feb 28 16:38	Mar 30 02:25
Places West of Greenwich
Rio de Janeiro¹	GMT - 2 hours	Dec 2 05:30	Dec 31 17:13	Jan 30 04:17	Feb 28 14:38	Mar 30 00:25
New York Toronto	GMT - 5 hours	Dec 2 02:30	Dec 31 14:13	Jan 30 01:17	Feb 28 11:38	Mar 29 21:25
Chicago Mexico City	GMT - 6 hours	Dec 2 01:30	Dec 31 13:13	Jan 30 00:17	Feb 28 10:38	Mar 29 20:25
Calgary Tucson	GMT - 7 hours	Dec 2 00:30	Dec 31 12:13	Jan 29 23:17	Feb 28 09:38	Mar 29 19:25
Los Angeles Vancouver	GMT - 8 hours	Dec 1 23:30	Dec 31 11:13	Jan 29 22:17	Feb 28 08:38	Mar 29 18:25
Hawaii	GMT - 10 hours	Dec 1 21:30	Dec 31 09:13	Jan 29 20:17	Feb 28 06:38	Mar 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 7 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!

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