For some people, Friday the 13th of September is a mystical sort of day. In addition to the mystery that surrounds Friday the 13th, tonight will also see a full moon. The last time a full moon and Friday the 13th coincided nationwide was October of 2000. According to the website earthsky.org, for those in the Northern Hemisphere, the full moon that will occur tonight counts as the closest full moon to the September autumnal equinox, making it a Harvest Moon. Are you wondering what constitutes a full moon? The moon appears full to the eye for a few to several days in succession when actually, it’s only truly full for a fleeting instant. Astronomically speaking, the moon is full at the moment that it’s exactly 180 degrees opposite the sun in ecliptic longitude. For time zones in the eastern United States, the full moon technically falls on Saturday, September 14th at 12:33 a.m. EST. In all other U.S. time zones, it falls on Friday, September 13th. The next time this rare phenomenon will happen is August 2049.