Cambodian New Year or Chaul Chnam Thmey in the Khmer language literally "Enter the New Year", is the name of the Cambodian holiday that celebrates the New Year. The holiday lasts for three days beginning on New Year's day, which usually falls on April 13th or 14th, which is the end of the harvesting season, when farmers enjoy the fruits of their labour before the rainy season begins. Khmers living abroad may choose to celebrate during a weekend rather than just specifically April 13th through 15th. (Read more of the Wikipedia entry.)
In Cambodia, Khmer New Year is the greatest traditional festival, and also the greatest national holiday. It is three days of festival and sometimes can be four days. Khmer New Year begins on April 13th or can begin on April 14th, depending on the "MohaSangkran," which is the ancient horoscope.
The Khmer New Year festival originated from Bramhmanism, a part of Hinduism, which was a religion that Khmer believed in before Buddhism. Later on, Buddhism became associated with the festival and then took all the important roles in the festivity.
Usually, Khmer New Year is celebrated for three days:
The first day of New Year is called Moha Sangkran, and it can be described simply as the inauguration of the New Angels who come to take care of the world for a one-year period. ...
The second day of New Year is called Wanabot, which means day of offering gifts to the parents, grandparents and elders. Usually, Khmer People like to share gifts or presents to employees and also donate money or clothes to poor people. In the evening, people go to temple to build a mountain of sand and ask the monks to give them a blessing of happiness and peace.
The third day is called day of "Leung Sakk;" that means the year starts to be counted up from this day, for example it is when the year of 2000 would change and begin to be 2001. Traditionally, in the morning, people would go to the temple to perform the ceremony of the mountain of sand to get blessed. In the evening, to complete the New Year festival, Khmer people need to perform the last ceremony, called "Pithi Srang Preah", which means giving a special bath or a special shower to Buddha statues, the monks, elders, parents and grandparents in order to apologize for any mistake done to them and to gratify them. Everyone has a wonderful time during this ceremony because it is a great opportunity for everyone, young and old, man and woman, to have much fun by spreading out water to each other.
(From Khmer New Year by Leng Lim, Secretary of Board of Directors of Khmer Community, Seattle, WA, April 2002. Read entire article here.)