How to find the dayname (sunday, monday etc.) of a given date?

Question

It can be a mathematical procedure. There's a guy I know who can tell the day of people's birthdays without even writing anything on a piece o paper.

Answer 1

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For a given date, we may need to know the day of the week. We have so many ways to find that. Here is one formula that can be used for the purpose, the only minor limitation is that it works only for the years of the Gregorian Calendar (greater than 1752).


n = (y + y/4 - y/100 + y/400 + t[m-1] + d) mod 7

n -> (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday) -> (0,1,2,3,4,5,6)


y -> Year

y/4 - y/100 + y/400-> Number of Leap Years

y/4 -> Number of leap years and exceptional common years

y/100 – y/400 -> Number of exceptional common years (The years that are divisible by 100 but not 400)

t[m-1] -> Constant corresponding to the particular Month
-> { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 }

d -> Date

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Answer 2

The first link below gives a procedure that you can use for year 1900 to 2099.
The 2nd link gives a more general procedure.

Answer 3

I have a littlle object with 3 cylinders which works for the years
1600 to 2299. Other than that...

How long does your guy take?

Answer 4

well, maybe,that guy your talking about is basing on last years day or the past year's dayname. Example, if April 10 today is Sunday, then next year it would be Saturday. But if its like this; today April 10 (sunday), next year(leap year) january 10 (friday) if today's year April 12 is friday next year its 1day before friday, but if its a leap year it should be like this; if January 12 is friday then next year April 12 would be 1+1 day before friday.

Answer 5

Go to a search engine and search for the month of the year in question and it will give you a site that shows the whole month.

Answer 6

that guy has probably autism

anyway, there's somekind of formula for it
http://www.cs.usyd.edu.au/~kev/pp/TUTORIALS/1b/carroll.html