How to solve calendar mathematics is a great fun. Here you will get the idea about how to solve calendar math problems and can help yourself find the day of a week for both Ordinary Year and Leap Year and even find the day of the week without knowing any particular given dates.
Days Gain or Loss
When we move forward or backward by 1 year, then 1 day is gained or lost.
Example: 8th July 2014 was Friday, then 8th July 2015 would be = Friday + 1 = Saturday.
If 4th February 2014 was Monday, then 4th February 2013 would be = Monday - 1 = Sunday.
When we move forward or backward by 1 leap year, then 2 days are gained or lost.
Example: 24th December 2011 was Tuesday, then 24th December 2012 would be
Tuesday + 2 = Thursday.
If 17th December 2012 was Tuesday, then 17th December 2011 would be
Tuesday - 2 = Sunday.
[Note: For finding the days in leap years the day must have crossed 29th of February, or else 1 should be added instead of 2.]
- Find a Particular Day on the basis of Given Day and Date
If 5th March 1999 was Friday, what day of the week was it on 9th May 2000?Ans: The number of days between 5th March 1999 and 9th May 2000,
Since 5th March 1999 was Friday then 5th March 2000 would be
Friday + 2 = Sunday
[2000 is leap year and 5th March has crossed 29th February.]
After 5th March 2000 we have 26 days of March + 30 days of April + 9 days of May = 65 days.
In 65 days we have 9 weeks and 2 odd or extra days.
So, 5th March 2000 is
Sunday + 9 Weeks
= Sunday + 2 odd or extra days
= Tuesday.
- Find a Particular Day without Given Date and Day
Mahatma Gandhi was born on 2nd October 1869. What was the day of the week?Ans: The nearest Century to 1869 is 1600.
To come to 1869 we have 1600 + 200 + 68
1600 = 0 odd days
200 = 3 odd days
68 = (17 leap year + 51 ordinary year)
So, 1600 + 200 + 68 = Sum of odd days
= 0 + 3 + (17*2 + 51*1)
= 0 + 3 + 85 = 88
= 12 weeks + 4 odd day (88/7= 12 wk + 4 days)
Now total odd days from January to 2 October of 69 or 1869
(odd days are derived by dividing total days of a month by 7, and the remaining are odd days)
January = 3 February = 0
March = 3 April = 2
May = 3 June = 2
July = 3 August = 2
September = 2 October = 2 (up to birth day date)
Total days = 23 = 3 weeks + 2 odd days
So, 4 odd days + 2 odd days = 6 days.
Therefore, 2nd October 1869 is Saturday.
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