Here’s Why The Full Moon Tonight Is Actually The Last Of The Decade

Tonight will bring an interesting full moon to the sky over the Magic Valley. It may not really look interesting as far as a full moon goes, but the history of this moon is what will be interesting and possibly a source of contention.

The EarthSky website has some interesting details about tonight's full moon. Since winter just began a few days ago with the winter solstice, our nights are longer so this full moon will be in the sky longer than any other full moon. The moon will officially be full tonight, December 29th, starting at about 7:30pm. The reason this full moon could be a source of contention depends on your idea of when a decade officially begins and ends.

Some are calling this full moon the final one of the decade while others say the final full moon was last year. For many, the new decade begins with the 'Zero' year through 'Nine': example 1980 through 1989. That makes sense because you would call that decade the 80's. For others though, what EarthSky calls the 'purists', the decade actually begins with the 'One' year, since there was never a year Zero. So a true decade time frame would be 1981 through 1990. For the purists, the new decade begins in 2021 and for the rest of us it began with 2020 and we already had the final full moon of the decade December 12th, 2019.

To be honest I hadn't thought about how I view my decades. I get the view of the 'purists' but I view decades as being from year 0-9. How do you determine when a decade begins and ends?