Once In A Blue Moon

Look out for NYE bluemoon tomorrow. This New Year's Eve blue moon will be visible in the United States, Canada, Europe, South America and Africa but for Australia and Asia, the full moon does not show up until New Year's Day, making January a blue moon month for them. The last time there was a "blue moon" was in May 2007. New Year's Eve blue moons are rarer, occurring every 19 years. The last time was in 1990; the next one won't come again until 2028. SOURCE

*A blue moon is a full moon that is not timed to the regular monthly pattern. Most years have twelve full moons which occur approximately monthly, but in addition to those twelve full lunar cycles, each solar calendar year contains an excess of roughly eleven days compared to the lunar year. The extra days accumulate, so that every two or three years (on average about every 2.7154 years[1]), there is an extra full moon. The extra moon is called a "blue moon." Different definitions place the "extra" moon at different times.