Why is Khmer New Year in April?

Many Cambodians have a lot of freedom to celebrate multiple New Years.  This includes the western New Year at the end of December, the Chinese New Year typically around February, and the Cambodian New Year in mid-April.  The Cambodian New Year is one of the biggest celebrations for Cambodians. The celebration lasts for 3 days with activities ranging from traditional ceremonies at the temple to activities within the families and friends.  It seems odd since the New Year's day is not the beginning of the year in the calendar they use including the Khmer lunar calendar.  So most people even Cambodians ask why do Cambodians celebrate New Year in April?

A typical response is because Khmer farmers are done with the rice harvesting in April and have spare time to relax and celebrate.  So the Khmer King in the Ankorian period chose this system.  This explains the civic reason why we choose this April New Year system, but it does not answer why this system picks the New Year to be in April.  

Some says that Khmer New Year calculation is based on the lunar calendar. This assumption is not correct since Khmer chankiteck calendar end the year in December or January. According to Zhou Daguan who is a Chinese traveler to Cambodia in the 13th century, Khmer celebrated New Year in the tenth month of the Chinese calendar. By using the computer to calculate the corresponding Khmer lunar month for that year, I found that it corresponds to the first month of Khmer lunar calendar in 1295, the year that he visited Cambodia.  So Khmer used to celebrate New Year using the lunar calendar system.

Only at later part of the Ankorian period that Khmer changed the New Year to mid-April. By looking into other type of calendar, I found that Hindu calendar has their New Year or Songkran in April.  Khmer has long history of adopting many customs from India including Buddhism. Thus, it is safe to conclude that we adopted this system for celebrating the New Year.

The first day of Khmer New Year or Songkran is calculated based on the Reaseys. Reaseys are the divisions of the path of the Earth around the sun based on the star constellation. Mesa or April Reasey correponds to the Songkran star which is considered to be the star that divides the old year and the new year. When the earth first enters the Mesa Reasey, it is called Songkran (the first day of the New Year). It falls on April 13 or 14 of Gregorian calendar in recent years. See a list of the Songkran New Year dates.

Khmer Songkran calculation is different than the Hindu calculation. From my study, it varied between 10 to 70 minutes. The exact calculation of Khmer Songkran is done by Khmer Horas or astronomers. Khmer Hora such as Mr. Borin Im would publish the exact Songkran time which is believed to be the time that New Year angels make their procession down to Earth. He would describe the angel that represent the year with other predictions related to the Khmer New Year customs.