Blue Moon - The Double Blue Moon of 2018

Our Blue Moon Calculator says that in 2018, there is a double Blue Moon: both January and March have two Full Moons. This is true for most of the world, but not New Zealand, whilst in eastern Australia, things get a bit complicated.

Let's start with the basic astronomical facts. The Full Moons for January 2018 to April 2018 are as follows:

2 January 2018	at	02:24 UTC
31 January 2018	at	13:26 UTC
2 March 2018	at	00:51 UTC
31 March 2018	at	12:37 UTC
30 April 2018	at	00:58 UTC

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 Coordinated Universal Time (UTC) which is the standard time zone used by astronomers worldwide. It is effectively the same as Greenwich Mean Time.

Here are those five 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	Standard Time Zone	Full Moon 1	Full Moon 2	Full Moon 3	Full Moon 4	Full Moon 5
Places East of Greenwich
Auckland	UTC + 12 hours	Jan 2 15:24¹	Feb 1 02:26¹	Mar 2 13:51¹	Apr 1 01:37¹	Apr 30 12:58
Sydney	UTC + 10 hours	Jan 2 13:24¹	Feb 1 00:26¹	Mar 2 11:51¹	Mar 31 23:37¹	Apr 30 10:58
Brisbane	UTC + 10 hours	Jan 2 12:24	Jan 31 23:26	Mar 2 10:51	Mar 31 22:37	Apr 30 10:58
Adelaide	UTC + 9 hours 30 minutes	Jan 2 12:54¹	Jan 31 23:56¹	Mar 2 11:21¹	Mar 31 23:07¹	Apr 30 10:28
Tokyo	UTC + 9 hours	Jan 2 11:24	Jan 31 22:26	Mar 2 09:51	Mar 31 21:37	Apr 30 09:58
Perth	UTC + 8 hours	Jan 2 10:24	Jan 31 21:26	Mar 2 08:51	Mar 31 20:37	Apr 30 08:58
Kolkata	UTC + 5 hours 30 minutes	Jan 2 07:54	Jan 31 18:56	Mar 2 06:21	Mar 31 18:07	Apr 30 06:28
Karachi	UTC + 5 hours	Jan 2 07:24	Jan 31 18:26	Mar 2 05:51	Mar 31 17:37	Apr 30 05:58
Moscow	UTC + 3 hours	Jan 2 05:24	Jan 31 16:26	Mar 2 03:51	Mar 31 15:37	Apr 30 03:58
Johannesburg	UTC + 2 hours	Jan 2 04:24	Jan 31 15:26	Mar 2 02:51	Mar 31 14:37	Apr 30 02:58
Paris	UTC + 1 hours	Jan 2 03:24	Jan 31 14:26	Mar 2 01:51	Mar 31 14:37¹	Apr 30 02:58¹
The Greenwich Meridian
London	UTC	Jan 2 02:24	Jan 31 13:26	Mar 2 00:51	Mar 31 13:37¹	Apr 30 01:58¹
Places West of Greenwich
Sao Paulo	UTC - 3 hours	Jan 2 00:24¹	Jan 31 11:26¹	Mar 1 21:51	Mar 31 09:37	Apr 29 21:58
Halifax	UTC - 4 hours	Jan 1 22:24	Jan 31 09:26	Mar 1 20:51	Mar 31 09:37¹	Apr 29 21:58¹
New York	UTC - 5 hours	Jan 1 21:24	Jan 31 08:26	Mar 1 19:51	Mar 31 08:37¹	Apr 29 20:58¹
Chicago	UTC - 6 hours	Jan 1 20:24	Jan 31 07:26	Mar 1 18:51	Mar 31 07:37¹	Apr 29 19:58¹
Edmonton	UTC - 7 hours	Jan 1 19:24	Jan 31 06:26	Mar 1 17:51	Mar 31 06:37¹	Apr 29 18:58¹
Los Angeles	UTC - 8 hours	Jan 1 18:24	Jan 31 05:26	Mar 1 16:51	Mar 31 05:37¹	Apr 29 17:58¹
Hawaii	UTC - 10 hours	Jan 1 16:24	Jan 31 03:26	Mar 1 14:51	Mar 31 02:37	Apr 29 14:58
¹ Daylight saving time is in effect.

As you can see, Europe, Africa, the Americas and Asia have a Double Blue Moon in 2018. So does western and central Australia, as well as the state of Queensland in eastern Australia and the town of Broken Hill in New South Wales.

However, eastern Australia (except Queensland and Broken Hill) and New Zealand have only one Blue Moon. It falls in March in eastern Australia (except Queensland and Broken Hill) and in April in New Zealand. This happens because the Full Moons which the rest of the world sees on January 31 and March 31 are shifted to the following month in time zones that are 11 or more hours ahead of UTC.

What is special about Queensland? It doesn't observe daylight saving time, so it is only 10 hours ahead of UTC whilst the other states of eastern Australia are 11 hours ahead.

And Broken Hill, a mining town in western new South Wales, keeps the same time as South Australia, so it is 10.5 hours ahead of UTC in summer and 9.5 hours ahead during the rest of the year.

Once in a Blue Moon

The Double Blue Moon of 2018