The date of Easter
Fixing the date triggered a major controversy in early Christianity, known as the Paschal controversies, which was not definitively resolved until the 8th century. Britannica Scholars: Easter In Asia Minor, Christians observed the day of the Crucifixion on the same day that Jews celebrated the Passover offering, on the 14th day of the first full moon of spring, 14 Nisan. Britannica Scholars: Easter
In the West the Resurrection of Jesus was celebrated on the first day of the week, Sunday, and Easter was always celebrated on the first Sunday after the 14th day of the month of Nisan. Britannica Scholars: Easter The churches increasingly opted for the Sunday celebration, and the Quartodecimans ("14th day" proponents) remained a minority. Britannica Scholars: Easter
The Council of Nicaea in 325 decreed that Easter should be observed on the first Sunday following the first full moon after the spring equinox (March 21). Britannica Scholars: Easter Easter, therefore, can fall on any Sunday between March 22 and April 25. Britannica Scholars: Easter
The World Council of Churches states that the Council of Nicaea established that the date of Easter would be the first Sunday after the full moon following the vernal equinox. World Council of Churches
West and East
Eastern Orthodox churches use a slightly different calculation based on the Julian rather than the Gregorian calendar, with the result that the Orthodox Easter celebration usually occurs later than that celebrated by Protestants and Roman Catholics. Britannica Scholars: Easter The Orthodox churches still use the Julian calendar to calculate the vernal equinox and the full moon that follows it, which is why they calculate a different date. World Council of Churches
At present, the Julian calendar is running 13 days "slow" of the Gregorian; by the year 2100, the difference will be 14 days. World Council of Churches The gap between the two Easters is different every year. It can be as much as five weeks. World Council of Churches
Moreover, the Orthodox tradition prohibits Easter from being celebrated before or at the same time as Passover. Britannica Scholars: Easter
Orthodox Easter and Passover
Britannica says the Orthodox tradition prohibits Easter from being celebrated before or at the same time as Passover. The World Council of Churches, discussing the Nicaea rule, says today's theologians are no longer entirely certain what was meant by not celebrating Easter "with" the Jews, but that Orthodox Easter still cannot fall on the same day as Passover, and is postponed by a week if it does. We give each source its own wording and do not flatten them into one rule.
In the 20th century several attempts were made to arrive at a fixed date for Easter, with the Sunday following the second Saturday in April specifically proposed. While this proposal and others had many supporters, none came to fruition. Britannica Scholars: Easter Renewed interest in a fixed date arose in the early 21st century, from discussions involving the leaders of Eastern Orthodox, Syriac Orthodox, Coptic, Anglican, and Roman Catholic churches, but formal agreement on such a date remained elusive. Britannica Scholars: Easter
A coming Western date
Timeanddate gives Easter Sunday 2027 in the United Kingdom as Sunday, 28 March 2027. Timeanddate: Easter Sunday UK
That is a Western, Gregorian date. It is not, on its own, a statement of the Orthodox date for the same year.