How to calculate Calendar Dates? -
August 22nd, 2006
The questions of calculating calendar dates usually comes in CAT etc..........
many of you may know many tricks of calculating calendar dates and those may be easy than the following method but this method also buits up the calculation speed as a whole...........
u may do one thing: now as u r sitting in front of the pc , click on the time display of the taskbar............a window will open in which there is diplay of a watch n a calendar.............. while seeing the watch and stare at any date in the calendar and apply the following method to arive at its day..............
religiuosly follow this and u may increase ur speed of calculation.............change the calendar and utilise the method...........i have devised this method to improve my speed ( the method of calculation is not mine but theWCT watch,calendat taskbar method is mine)............
the method is as follows:
What day of the week will May 12, 2034 be? What day of the week was May 12, 1298? Here's a neat algorithm that will tell you:
(Note: all divisions, except where noted otherwise, are integer divisions, in which remainders are discarded.)
First figure out the values for a, y, and m -- variables to be plugged into a formula.
a = (14 - month)/12 (month = # of month, 1 for Jan, 2 for Feb, etc)
y = year - a (year = the 4 digit year)
m = month + 12a - 2
Next, plug the values of y and m into the following formula to calculate the day:
d = (day + y + y/4 - y/100 + y/400 + 31m/12) mod 7
(Note: mod 7 means "modulo division." That is, take the remainder instead of the quotient as your answer. For example, 20 mod 3 = 2, because the remainder is 2.)
The answer you get for d will correspond to a day of the week as such:
0 = Sunday
1 = Monday
2 = Tuesday
3 = Wednesday
4 = Thursday
5 = Friday
6 = Saturday
Here's an example.
What day of the week will April 5, 2020 fall on?
First figure out a, y, and m:
a = (14 - 4)/12 = 0 (remember, it's integer division so remainders are discarded. 4 represents the month of April since it's the fourth month of the year.)
y = 2020 - 0 = 2020
m = 4 + 12(0) - 2 = 2
Now plug y and m into the d formula to calculate the day:
d = (5 + 2020 + 2020/4 - 2020/100 + 2020/400 + 31(2)/12) mod 7
d = (5 + 2020 + 505 - 20 + 5 + 5) mod 7
d = 2520 mod 7
d = 0 (2520/7 = 360 with a remainder of 0)
Recall from above that 0 = Sunday. So April 5, 2020 will be a Sunday.
Cool, huh? Remember, you can do this for dates in the past as well.
(COURTESY CURIOUS MATH)