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Your search for Why do Catholicism and Orthodox Christianity have different dates for Easter returned the following results:

from the dates used by western churches

The Orthodox Easter dates usually differ from the dates used by western churches because most Orthodox churches retained some version of the Julian calendar, which is older than the Gregorian calendar, commonly used today.

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most Orthodox churches retained some version of the Julian calendar

The Orthodox Easter dates usually differ from the dates used by western churches because most Orthodox churches retained some version of the Julian calendar, which is older than the Gregorian calendar, commonly used today.

because of differing calendars

However, as discussed above, Eastern Orthodox and Western/Eastern Catholic Easter falls on different dates because of differing calendars.

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Due To The Use Of The Julian Calendar By The Former And The Gregorian

The Difference In Dates Between Orthodox Easter And Easter Is Due To The Use Of The Julian Calendar By The Former And The Gregorian.

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For this reason

For this reason, Orthodox Easter generally falls on a different date than the Western Christian Easter.

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from the Western Church

Often, the dates for Easter, as followed by the Eastern Church (Orthodox) differ from the Western Church.

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of Passover

The difference in the determination of Easter between the Orthodox and other Christian Churches concerns the date of Passover.

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In eastern orthodox christianity, and

In eastern orthodox christianity, and for some byzantine catholics, the date for easter (called pascha in orthodox traditions) often differs from the western date.

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from the Catholic ones

(Note that Orthodox dates for Easter may differ from the Catholic ones).

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by the secular press

The difference in the dates that Orthodox Christians celebrated Christmas and Easter was often noted with perplexity by the secular press.

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