atmosphere by fires and storms usually contain a mixture of particles with a wide range of sizes, with most smaller than 1 micrometer, and they tend to scatter blue light. This kind of cloud makes the moon turn red; thus red moons are far more common than blue moons. Blue moons between 2009 and 2037 The following blue moons occur between 2009 and 2021. These dates use UTC as the time zone; exact dates vary with different time zones. Seasonal Using the Maine Farmers' Almanac definition of blue moon (meaning the third full moon in a season of four full moons, but referenced to astronomical rather than equal seasons), blue moons have occurred on: November 21, 2010 August 20, 2013 May 21, 2016 May 18, 2019 Aug 22, 2021 Calendar Unlike the astronomical seasonal definition, these dates are dependent on the Gregorian calendar and time zones. These blue moons cannot occur in February. Two full moons in one month (the second of which is a "blue moon"): A blue moon can occur in January and the following March if there is no full moon at all in February, as is the case in the years 1999, 2018, and 2037. 2009: December 2 and 31 (partial lunar eclipse visible in some parts of the world), only in time zones west of UTC+05 2010: January 1 (partial lunar eclipse) and 30, only in time zones east of UTC+04:30 2010: March 1 and 30, only in time zones east of and including UTC+07 2012: August 2 and 31, only in time zones west of and including UTC+10 2012: September 1 and 30, only in time zones east of and including UTC+10:30 2015: July 2 and 31 2018: January 2 and 31 (total lunar eclipse visible in some parts of the world), only in time zones west of and including UTC+11 2018: March 2 and 31, only in time zones west of and including UTC+12 2020: October 1 and 31, only in time zones west of and including UTC+10 2020: November 1 and 30 (penumbral lunar eclipse visible in some parts of the world), only in time zones east of and including UTC+9 2028: December 2 and 31 (total lunar eclipse visible in some parts of the world), only in time zones west of UTC+8 2029: January 1 (total lunar eclipse) and 30, only in time zones east of UTC+7 2037: January 1 and