Easter is not held on the same date every year. This is called a "moveable feast". Currently all Christian churches agree on how the date is calculated. Easter is celebrated on the first Sunday following the first full moon which is on or after March 21st. This means it is celebrated in March or April. It can occur as early as March 22 and as late as April 11. Western churches, like the Roman Catholic Church, use the Gregorian calendar, while Eastern churches, like the Eastern Orthodox Church, use the Julian calendar. Because of this, the date of Easter celebrations is different for these two types of churches even though the way they calculate the date is similar. In 2015 Easter was celebrated on April 5 for both the Gregorian calendar and Julian calendar. In 2019 Easter was celebrated on the 21st of April.