Blue Moons sound poetic and beautiful but they are not for real. At least, they don’t count for anything in astrology. Why so?
The definition of a Blue Moon is simply that it is the second of two Full Moons in one calendar month. A calendar month is astrologically irrelevant. Once upon a time, all months WERE the Moons.
The reason why “13” became an “unlucky” number to the Christians & Patriarchs is because there are actually 13 months in a year – 13 Moon cycles in one of the Earth’s rotations around the Sun aka a year.
Months began with the New Moon and ended with the last day of the Dark Moon before the New Moon. That this lined up with womens menstruation cycles was not lost on people. The very term comes from “Mensa” – the goddess of measurement.
Various patriarchs fiddled with the months – adding on days here, subtracting them there, naming some after Emperors (Augustus, for example) instead of deities – and so we have our contemporary calendar months. They are a conceit. If there are two Full Moons in a calendar month, so what?
What really counts with a Full Moon is how closely it is aligned with a planet like Pluto, whether it is intensified by being an Eclipse or if it is pinging off something in your personal natal birth energies.