Monday, May 18, 2015

Dooms Day Algorithm to Find Week Day of Given Date

        Using Dooms Day Algorithm / Rule any one can find the week day of given date between 1800 - 2199 years. So, The dooms day rule / formula is as follows

Dooms day = Anchor Day + [Year/12] + Remainder[Year/12] + [Remainder[Year/12]]/4

If the given date's year falls,

between 1800-1899, The Anchor Day is Friday
between 1900-1999, The Anchor Day is Wednesday
between 2000-2099, The Anchor Day is Tuesday
between 2100-2199, The Anchor Day is Sunday 

In the Above formula Year is last 2 digits of given date's year and in above equation solving wherever we get decimal values we have to take integer values only.

Once we get the dooms day for the given date's year using above formula, that dooms day will fall on last day of February (if given year is normal year on Feb 28, otherwise Feb 29), April 4 (4/4), June 6 (6/6), August 8 (8/8), October 10 (10/10) and December 12 (12/12).

Example: Lets find the week day of August 15, 1947.

The given date's year 1947 falls between 1900-1999 so the Anchor day is Wednesday.

Dooms day = Wednesday + [47/12] + Remainder[47/12] + [Remainder[47/12]]/4

Dooms day = Wednesday + 3 + 11 + 2

Dooms day = Wednesday + 16 (Divide this number by 7 and take remainder to find number of odd days)

Dooms day = Wednesday + 2 = Friday.

So the Dooms day for year 1947 is Friday and It will fall on August 8 as I said earlier. So, If August 8 is Friday after one week i.e., on August 15 is also going to be Friday.

So finally August 15, 1947 is Friday :-).

No comments:

Post a Comment