EASTER DATES

Q.So how is the date of Easter calculated?
A.The council of Nicaea established that the date of Easter wouuld be the  1st Sunday after the full moon following the vernal equinox.
Q. Why,then despite the universal rule laid down at Nicaea,to different parts of the church   still  celebrate Christs resurrection  at different dates?
A.The first thing to remember is that even after the council of Nicaea,differences in the date of Easter remained ,since the council had said nothing about the methods to be used to calculte the timing of the full moon or the vernal equinox.But the real problem behind the situation we have today arose in the 16th century,when the Julian calendar,which had been established in 46BC,was superseded by the Gregorian calendar.It took some time for new calendar to be adopted by all countries(it did not happen in Greece until the start of 20th century).However the Orthodox churches still use the Julian calendar to this day to calculate the vernal equinox and the full moon that follows it.This is why they calculate a different date.