Day of the Date - Funny Math Shortcut

Learn here some shortcuts/tips to find out the day of the week from the given date. The trick is done by memorizing or having the pre-defined offset table value for century, month and week days. You can find the of any past year or forth coming years at random using this simple trick. Play this trick with your parents or friends and prove your talent to them by following the step by step instructions. This is a funny math shortcut and tip to find the day of the date.

Day of the Date

Finding Number of Months

Century offset calculation (Gregorian Calendar):
Step1 :Take the first two digit of the given year.
Step2 :Calculate the next highest multiple of 4 for the first two digit number.
Step3 :Subtract 1 from the number.
Step4 :Then, subtract the first two digit from the number.
Step5 :Finally, multiply the resultant value with 2.


Example:

Calculate century offset for 1900s century.
Let us take the first two digit 19.
The next highest multiple of 4 for the first two digit number 19 is 20.
Subtract 1 from the number. i.e. 20-1
Subtract the first two digit of the given number i.e ((20-1)-19)
Finally, multiply the resultant value with 2..
1900s = ((20-1)-19)*2 = 0.
Below given Gregorian Century Offsets table shows the other century and offset values,

CenturyOffset
300, 700, 1100, 1500,1900, etc.0
400, 800, 1200, 1600, 2000, etc.6
100, 500, 900, 1300, 1700, etc.4
200, 600, 1000, 1400, 1800, etc.2

Find The Year Offset:
Year Offset = ( Last two digit of year + (Last two digit of year / 4) ) mod 7
Note : If the given year is leap year and month is Jan/Feb, then the Year Offset = ( ( Last two digit of year + (Last two digit of year / 4) ) mod 7 ) - 1

Find the Month Offset:
Consider there are 4 weeks in a month, which means 4 x 7 = 28 days. January has 31 days. The days remaining are 31-28=3. The reminder helps you in calculating the numbers for each month.
Initially, Take Jan as 0
February = ( Number of days in Jan + Remaining days in Jan ) / 7) = (31+0)/7 = 3
March = ( Number of days in Feb + Remaining days in Feb ) / 7) = (28+3)/7 = 3
April = ( Number of days in Mar + Remaining days in Mar ) / 7) = (31+3)/7 = 6
Continue the same process till December... The numbers for the months are,


Month Offsets table:
MonthOffset
January0
February3
March3
April6
May1
June4
July6
August2
September5
October0
November3
December5

Numbers for the weekdays are,

Sunday0
Monday1
Tuesday2
Wednesday3
Thursday4
Friday5
Saturday6

You are about to remember this table before proceeding with the trick.
Now let us play the trick

Remember the formula Century offset + Year offset + Month offset + Day Offset
Where,

Day Offset = Given day mod 7
Year Offset = ( Last two digit of year + (Last two digit of year / 4) ) mod 7
if the given year is leap year and month is Jan/Feb, then Year Offset = ( ( Last two digit of year + (Last two digit of year / 4) ) mod 7 ) - 1
Step1: Ask for any specific date and challenge them you could tell the weekday of the date mentioned without any calculation. Example: 5th sep 2016
Step2: Take the century offset from the first table, 2000 is 6.
Step3: Calculate the year offset for 86 is ((16 + 16/4) mod 7) = 6
Step4: Take the month offset from the second table, June is 5.
Step5: Calculate the day offset, that is 5 mod 7 = 5
Step6: Now add all the 4 numbers: 6 + 6 + 5 + 5 = 22.
Step7: Divide 22 by 7 = 1 remainder 1.
The reminder tells you the day.
Answer: Monday

Finding the day of the date a funny tricky play of maths. Enjoy it with Fun!


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