Whether they belong to the Ukrainian Catholic church, the Ukrainian Orthodox church, or a Protestant denomination, this spring festival celebrates the central event of the Christian faith—the resurrection of Christ three days after his death by crucifixion.
So in 1582, Pope Gregory created a calendar that corrected the discrepancy and would be more accurate going forward. This new calendar was called the Gregorian calendar, named for its creator.
The western world quickly adopted the new calendar. But Eastern rite churches had been aligned with Constantinople, not Rome, since the Great Schism of 1054. They were having none of this "new" calendar created by who they considered merely a "Bishop of Rome."
Shortly afterward, matters got more complicated, with the creation of the Ukrainian Catholic (Eastern) Rite. In 1596 some Ukrainian clerics switched their allegiance to Rome while retaining the religious doctrines and practices of the Orthodox faith,
While this new schism created political tension amongst Ukrainian Christians, they were nonetheless united when it came to following the Julian calendar while the western world followed the Gregorian.
That wasn't a problem at first, as the two worlds didn't intersect much. But of course that wouldn't last.
On March 1, 1918, the Central Rada (parliament) of the then short-lived independent Ukrainian state introduced the Gregorian calendar into civil life. Attempts to introduce it into the church were met with fierce resistance from the people, however. So the Ukrainian Orthodox and Greek Rite Catholics churches continued to follow the Julian calendar for religious holidays.
A few weeks earlier, on January 24, 1918, the Bolsheviks officially decreed the change in Soviet Russia from the Julian to the Gregorian calendar. Ironically, the change was initiated by the Russian Orthodox church, which later reverted to the Julian calendar. The Soviet state of course stuck with the Gregorian calendar.
In the mid- and late 20th century, the Ukrainian Catholic church in Canada and other diaspora communities started to make the switch to the Gregorian calendar. This happened at varying times starting from 1941, after the church received permission in 1936 to make the switch.
Today, a few Ukrainian Catholic churches in Canada still follow the Julian calendar, but there is growing pressure (particularly in Eastern Canada) by the church hierarchy to change.
Meanwhile, the Ukrainian Orthodox church has traditionally stayed with the Julian calendar, along with other Orthodox churches.
However, the Orthodox are also under pressure to change. In 1923 a revised calendar was introduced at an inter-Orthodox congress in Constantinople (now Istanbul). This revised calendar is virtually identical to the Gregorian calendar, with the exception of Easter. In Canada some Orthodox follow this while others observe the original Julian calendar.
As a result of the calendar chaos, Ukrainian Christians celebrate Easter from one to five weeks apart, depending on their church.
Occasionally, however, Easter falls on the same day on both calendars. That has happened quite often in recent years—2010, 2011, and 2014.
As well, it falls on the same day, this year, 2017. The calendars won’t coincide again on Easter until 2025.
Whatever year or calendar, Ukrainian Easter is spectacularly beautiful, as you can see in these videos of Easter services in both Ukrainian Catholic and Ukrainian Orthodox churches.
Христос Воскрес! Воїстино Воскрес!