Today is the day of the Hindu festival Diwali, the festival of light. About 200m from my house is a Hindu temple, and it has been lit up for the last several days in celebration of this important Hindu festival. Here is a picture I took on Sunday evening.
Like most religions, with the exception of Islam, the Hindu calendar is a luni-solar calendar, and so the date of Diwali changes. Last year (2011) it was on the 26th of October, and next year (2013) it is on the 3rd of November, but this year it is today, the 13th of November. How is the date of Diwali calculated?
Being a luni-solar calendar, this means it follows something both the Moon and the Sun are doing. Today is a new Moon. So, the question is, what is special about today’s new Moon? What recent important Solar event happened? The Autumn equinox of course, which was on the 22nd of September this year (2012). The firsrt new Moon after this year’s Autumn equinox was on the 15th of October, and today is the second new Moon after the Autumn equinox. So, Diwali always falls on the 2nd new Moon after the Autum equinox! It’s that simple……
I wish a very happy Diwali to all my Hindu friends and students (and readers) around the World.