The Easter holiday always falls on a Sunday between March 22 to April 25. But how come it varies from year to year and isn’t always on the same day like Christmas? Certainly Easter is just as important as Christmas.
The date for Easter changes yearly in accordance with the Gregorian calendar. The current Gregorian ecclesiastical rules trace back to 325 AD when Roman Emperor Constantine convened the First Council of Nicaea. At that time Constantine decided the Roman Empire would use the Julian calender, offered up by Julius Caesar.
In 1582 Pope Gregory XIII reconstructed the Julian calendar into the Gregorian calendar, with such differences as the “leap year” inclusion. By the 18th century, the majority of Europe was using the Gregorian calendar.
The general rule of thumb is that Easter is always the Sunday after the first full moon post-vernal equinox. The vernal equinox (when night and day are the same length) is fixed at March 21st. This year Easter falls on April 8th, while next year will be March 23rd.
The ecclesiastical lunar cycles can be easily programmed to predict the date of Easter in future years. The US Navy has developed an algorithm that uses the Gregorian system to do just that.
Here is a reproduction of the US Navy algorithm to compute the day of Easter years in advance:
The algorithm uses the year, y, to give the month, m, and day, d, of Easter. The symbol * means multiply.
Please note the following: This is an integer calculation. All variables are integers and all remainders from division are dropped. For example, 7 divided by 3 is equal to 2 in integer arithmetic.
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 2010,
y=2010,
c=2010/100=20,
n=2010 - 19 x (2010/19) = 2010 - 19 x (105) = 15, [see note above regarding integer calculations]
etc. resulting in Easter on April 4, 2010.
13 Comments
quite interesting..its a weird thought that next year Easter will fall two weeks or so after St.Patrick’s Day
At last, an answer, I always ask myself this question around Easter time but never look into it.
Yea it’s pretty dee-zuhl, now you can calculate when Easter will fall whenever you want.
christine- it might be easier to see when next years Easter will be by looking at a calender
Although, without question, calculating Easter holiday dates is my new found hobby… I agree, I can never go through all the work just to find out when Easter falls
I will be 68 years old on April 8 of this year. I don’t remember if my birthday was ever on Easter before this year or not. Both of my parents are deceased and I have no one to ask about this. Many years ago, when I was just a teenager I met an older woman who had a callender that showed the dates of Easter for 100 years. I remember that she told me that my birthday would be on Easter Sunday when I was in my 60’s. I had actually forgotten that incident until now when my birthday is on Easter Sunday. My son-in-law says that his birthday falls on Easter Sunday next year. Does anyone know how to obtain that calender for the nineteen hundreds. Please advise me if you know. Thanks and Happy Easter
@ Sherrell - thanks for sharing your story and contributing to the site. While that formula listed above is very complex and kind of intimidating, you’re in luck, I stumbled across this Easter calculator that will tell you what day Easter falls on in any year from 326 to 4099 AD. Hope that helps, and Happy Birthday!
@ Sherrell - unfortunately I forgot to post it when I wrote that last night lol, here you go http://users.chariot.net.au/~gmarts/eastnet.htm
so when is easter next year? calculate THAT!
hi been trying to look into as to when the next easter will be on april 18th because back in 1965 april 18th I was born and that was on easter sunday. that was a special day you can look it up but yes it was easter on my birthday lol but wondering if or when will easter Sunday come back to April 18th can’t find what i am looking for and hope that you could help me with this thanks.
I noticed this: “In 1582 Pope Gregory XIII reconstructed the Julian calendar into the Gregorian calendar, with such differences as the “leap year” inclusion.” in your article and wanted to say that this is either wrong or ambiguously worded, depending on the author of the article actually meant.
To clarify: leap years have already been included in the Julian calendar. The fact of the matter is that Julian calendar stipulated for a leap year EVERY fourth year. Because Julian calendar was not quite synchronized with the actual length of the year, it was evident that there were too many leap years.
This is where Gregorian calendar comes in: it decreased the number of leap years. Every centennial year (i.e. one which is divisible by 100) is NOT a leap year except for years which are divisible by 400.
Therefore, Gregorian calendar actually added some “exclusions” to the 4-year leap year cycle, rather than the “inclusion” of leap year.
Google easter for 100 years it will give you all the dates
Someone had told em that this year easter would fall on March 20th (a thursday) because the numbers of days in a year are not correct. this meaning that every so many years it would not fall on a sunday but on a thusday….is this correct or no???