LENTEN AND EASTER CALCULATIONS

Photo: Marina Willats / Pinterest

Introduction

Why most Holy Weeks occur on April and rarely on March? How it's movable religious holiday?

Calculation

The calculation for Easter (and by extension Holy Week and Lent) is indeed based on the lunar cycle, specifically the Paschal Full Moon. According to the rules established by the Council of Nicaea in 325 AD, Easter falls on the first Sunday after the first full moon occurring on or after the vernal equinox. Easter Sunday is the primary anchor. It is the Sunday following the Paschal Full Moon, which in ecclesiastical rule, it must fall on or after March 21 unlike in the astronomical observations which fall either March 19 to 21. Because these calculations rely on the Metonic cycle (a 19-year lunar cycle), the dates for Lent and Holy Week "move" each year on our standard solar calendar. 

Rule

The Paschal Full Moon is the first ecclesiastical full moon that occurs on or after March 21. It is the celestial event used to determine the date of Easter in Western Christianity

If the Paschal Full Moon occurs on any day from Monday to Saturday, it falls directly within Holy Week. For Example, April 1, 2026 is the Paschal Full Moon, thus the Palm Sunday can be placed on March 29 to other Sunday on April 5. If the full moon itself falls on a Sunday, Easter is delayed by exactly one week to avoid coinciding with Passover. For Example, the April 13, 2025 is in Sunday and Paschal Full Moon, thus the same day as Palm Sunday and the other sunday is Easter Sunday, that's April 19, 2025.

After Holy Week Calculations, then it is proceed to calculate 46 days before as Ash Wednesday and 50 days after as Pentecost Sunday, 40 days after as Ascension of the Lord, and 60 Days after as Corpus Christi.

Reference

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‌Liturgical Year Calculator. (2026). Iccec.org. https://www.iccec.org/prayerandreadings/Seasons/

‌The Date of Easter. (n.d.). Aa.usno.navy.mil. https://aa.usno.navy.mil/faq/easter

‌When is Easter? (2025). Rmg.co.uk. https://www.rmg.co.uk/stories/time/when-easter

‌How are the dates for Easter, Palm Sunday, and Ash Wednesday determined? (n.d.). Catholic Answers. https://www.catholic.com/qa/how-is-easter-sunday-determined-palm-sunday-ash-wednesday

Holy Week | Overview & Days | Study.com. (2026). Study.com. https://study.com/academy/lesson/holy-week-days-celebrations-easter.html

‌https://www.facebook.com/HugotSem/posts/why-lent-and-holy-week-have-different-dates-each-yearmany-people-wonder-why-lent/1437867317719651/

Kelly, J. (2025, April 11). When is Palm Sunday 2025? See Holy Week dates for Easter, Maundy Thursday, Good Friday. The Oklahoman; Oklahoman. https://www.oklahoman.com/story/news/2025/04/11/when-does-lent-end-see-holy-week-dates-for-palm-sunday-easter-2025/83024836007/

‌Almanac, O. F. (n.d.). Easter and the Paschal Full Moon. Old Farmer’s Almanac. https://www.almanac.com/easter-paschal-full-moon

‌Ascension and Pentecost - The liturgical year - GCSE Religious Studies Revision - WJEC. (n.d.). BBC Bitesize. https://www.bbc.co.uk/bitesize/guides/zqttdxs/revision/7

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