Calendar

Calendar problems can be solved by the concept of odd days.
Odd Days : Number of days remained that are more than complete week cycles. For 10 days, 3 odd days are there (1 week + 3 days).
For 15 days, 1 odd day (2 weeks + 1 day).

Month	Days	Weeks	Odd Days
January	31	4	3
February	28	4	0 (ordinary); 1 (Leap)
March	31	4	3
April	30	4	2
May	31	4	3
June	30	4	2
July	31	4	3
August	31	4	3
September	30	4	2
October	31	4	3
November	30	4	2
December	31	4	3
1600 Years = 0 Odd Days
300 Years = 1 Odd Day

Day	Odd Days
Sunday	0
Monday	1
Tuesday	2
Wednesday	3
Thursday	4
Friday	5
Saturday	6

• Ordinary Year : Has 365 days. 1 Odd day (52 weeks + 1 day).
• Leap Year : Has 366 days. 2 Odd days (52 weeks + 2 days).
• Every 4^th century is a leap year except other centuries. 400, 800, 1200, 1600, 2000 etc. leap year.