The most important festivals in the Cambodian calendar for 2019:
January 1                   International New Year Day
January 7                   Victory Day Over Genocide
February 19                Meak Bochea Day: one of the most
                                   important events in Buddhism
April 14 - 16               Khmer New Year Day
                                  (Choul Chhnam Khmer):

                                   is celebrated with waterfights
May 1                         International Labor Day
May 13 - 15                Royal Birthday of the King Sihamoni:
                                   celebrated with fireworks on the
                                   TonleSap Lake
May 18                       Visakh Bochea Day: birthday of Boeddha:
                                  ( candle procession in Angkor Wat is beautifull)
May 20                       Day of Remembrance
May 22                       Royal Ploughing Day: colorful procession to
                                   pray for good rice planting
                                   (mainly Phnom Penh)
                                  (most special at Angkor Wat)
June 18                      Kings Mother Birthday
September 24            Constitutional Day
September 27            Ancestors Day
October 15                 Commemoration Day of King
                                   Norodom Sihanouk
October 29                 King Norodom Sihamoni's coronation day
November  9              Independence Day
Nov 10-11-12             Bon Om Tuk: Water Festival and
                                   Moon Festival
                                   Boat Racing: hotels across the country
                                   are quickly filled in this period

The highlighted are the most important in the calendar. There are also a number of religious holidays that are celebrated mainly in the temples. The date is often dependent on the lunar calender.