Every year, Palm Sunday falls on the Sunday before Easter. Easter is determined by establishing the date of the first full moon on or after the spring equinox and choosing the first Sunday that occurs after that full moon.
In 2016, the first full moon after the spring equinox is predicted to occur on Wednesday, March 23. Therefore, Easter is scheduled to occur on Sunday, March 27. In consequence, Palm Sunday is scheduled to occur on Sunday, March 20. The dates for Easter Sunday and Palm Sunday are fixed for several years in advance because of the predictability of moon phases.