The word Songkran is from the Sanskrit language and means the passage of the sun from one sign of the Zodiac to another. That means there are twelve Songkrans each year, but the significance of this Songkran (sometimes called Major Songkran to distinguish it from the others) is when the sun enters the sign of Aries the Ram. The particular event was also closely related to the Vernal Equinox. 

Celebrating New Year at the time of the Vernal Equinox was very common in the past. The Songkran celebration is similar to those of the Indian Holi Festival, the Chinese Ching Ming, and the Christian Festival of Easter. Indeed, April Fool’s Day probably originated as mocking those who didn’t accept the switch of New Year from April to January in France in the Sixteenth Century. 

In ancient times, the dates of Songkran and the Vernal Equinox would have been closer, but they have shifted due to an effect called procession, where the Earth wobbles on its axis over a 25,000 year period. 

The date was originally set by astrological calculations, but it is now fixed on 13 April. The festival may be extended if some of the celebrations fall over a weekend. 

In Thailand, New Year is now officially celebrated on January 1st, in line with almost all other countries. Songkran was the official New Year until 1888, when it was switched to a fixed date of April 1st. It wasn’t until 1940, that this date was then shifted to January 1st.