Easter Sunday Calculation

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Easter Sunday Calculation

Easter Sunday celebrates the day when Jesus Christ was resurrected. On Good Friday, Christ was crucified and then buried. But on the third day, he rose from the dead. Thus Easter Sunday is the most important date in the Christian calendar, far more important than even Christmas day - Jesus' birth.

Fewer than one person in a thousand could tell you how the date for Easter Sunday is determined and thus explain precisely why Easter falls on a different date each year. While many people will tell you the moon was a factor, few realize that the vernal equinox plays a crucial role in the calculation.

This simplistic calculation works for most years:

1) Start your calculation from the Vernal Equinox, which is usually on March 21st.

2) Consult a diary to determine the next full moon. Easter falls on the following Sunday.

The full, complex calculation.

Fortunately these extra nuances only come into play every 20 years or so.

For 2000 years it is the Church that calculates when Easter falls. They are the sole arbiters of this date. Their calculations fix the Vernal Equinox at March 21st, even if astronomically, it falls on March 20th. Moreover, the ecclesiastical full moon is always 14 days from the ecclesiastical new moon. This may vary by one day from the astronomical full moon.

There are two more variables. The international date line may potentially cause the full moon to fall on different days in different parts of the world. Finally some Eastern Churches use the Julian calendar instead of the more modern Julian calendar, this factor produces the biggest practical difference in the determination of Easter.

Formula to Calculate Easter

This formula calculates the date of Easter Sunday. The algorithm uses the y for year, m for month and d for the day of Easter. Note * means multiply and when you divide, discard any remainder, thus 11 / 5 = integer 2

c = y / 100
n = y - 19 * ( y / 19 )
k = ( c - 17 ) / 25
i = c - c / 4 - ( c - k ) / 3 + 19 * n + 15
i = i - 30 * ( i / 30 )
i = i - ( i / 28 ) * ( 1 - ( i / 28 ) * ( 29 / ( i + 1 ) ) * ( ( 21 - n ) / 11 ) )
j = y + y / 4 + i + 2 - c + c / 4
j = j - 7 * ( j / 7 )
l = i - j
m = 3 + ( l + 40 ) / 44
d = l + 28 - 31 * ( m / 4 )

For example, using the year 2009
y = 2009
c = 2009/100 = 20
n = (2009 - ((19 * (2009/19)) = 14
k = 79
i = 2009 - (2009/4 - (2009-79) /3 + 19 * 14 + 15

....

m = 4

d = 12

®

Easter Day

2007 April 8th

2008 March 23rd (Very early)

2009 April 12th

Easter Date Trivia

As mentioned earlier, Easter Sunday is set by the 1st full moon after the Spring Equinox (which is March 20). Here's the interesting info. This year 2008 is the earliest Easter any of us will ever see the rest of our lives! And only the most elderly of our population have ever seen it this early (95 years old or above!). And none of us have ever, or will ever, see it a day earlier! Here's the facts:

1) The next time Easter will be this early (March 23) will be the year 2228 (220 years from now). The last time it was this early was 1913 (so if you're 95 or older, you are the only ones that were around for that!).

2) The next time it will be a day earlier, March 22, will be in the year 2285 (277 years from now). The last time it was on March 22 was 1818. So, no one alive today has or will ever see it any earlier than this year!

Days derived from Easter

Palm Sunday is the Sunday before Easter

Mothering Sunday (UK) 3 weeks before Easter

Ash Wednesday, which marks the start of lent is 46 days before Easter. The calculation of 40 days for lent discounts Sundays, thus explaining the discrepancy between 46 and 40.

See more Saints Days and other special days :

● Special Days ● St David's Day ● St Patrick's Day ● St George's Day ● St Andrew's ● Home

● Burns Night ● Up-Helly-Aa ● Groundhog ● Shrove Tue ● Candlemas ● Lady Day ● May Day

● 4th July ● Bastille Day ● St Swithin's ● Lammas ● Labor Day ● Michaelmas ● Remembrance

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