Once in a Blue Moon

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 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!