Calendar Problems(Tricks and Tips)
Students frequently find calendar problems to be perplexing. Using the proper strategies, calendar problems can be readily resolved. Remember that with consistent effort and practice, you can attain perfection.
How to find the day of any date from the year 1900 to 2099?
What is a Calendar?
A calendar is a visual representation of the days, weeks, and months of a specific year.
- 1 week = 7 days
- 1 month = 4 weeks
- 1 year = 365 or 366 days = 52 weeks + 1 extra day or 52 weeks + 2 extra days.
There are 365 days in a typical year and 366 in a leap year. Once every four years, we have a leap year.
Leap year check:
Example:
Suppose the given year is 2004, 2004 is divisible by 4 and not by 100. Therefore, it is a leap year.
If the given year is 2000, 2000 is divisible by 4 and 100. Further verification is needed to check the divisibility of 2000 by 400. 2000 is also divisible by 400. Therefore, 2000 is a leap year.
☀ In general centuries needed double verification.
Code Number for days:
There are few codes to memorize are given here to solve the calendar problem easier.
| Days | Code |
|---|---|
| SUNDAY | 0 or 7 |
| MONDAY | 1 |
| TUESDAY | 2 |
| WEDNESDAY | 3 |
| THURSDAY | 4 |
| FRIDAY | 5 |
| SATURDAY | 6 |
Code Number for Months:
Codes to memorize for months are as follows
| Month | Code |
|---|---|
| JANUARY | 6 for the Normal year and 5 for the Leap year |
| FEBRUARY | 2 for the Normal year and 1 for the Leap year |
| MARCH | 2 |
| APRIL | 5 |
| MAY | 0 |
| JUNE | 3 |
| JULY | 5 |
| AUGUST | 1 |
| SEPTEMBER | 4 |
| OCTOBER | 6 |
| NOVEMBER | 2 |
| DECEMBER | 4 |
Year code:
We need specific steps of calculations to find the year code for the years 2000 to 2099:
Step 1:
First divide the last two digits by 4
Ignore the remainder, add the quotient to the last two digits.
Step 2:
Now divide the obtained number by 7. The remainder gives the year code.
Example:
Find the year code for 2020?
Step1:
20/4 = 5, remainder = 0
20+5=25
Step 2:
25/7, remainder = 4
Therefore, the year code for 2020 is 4.
Calculating the year code for the years 1900 to 1999:
Step 1:
First divide the last two digits by 4
Ignore the remainder, add the quotient to the last two digits and add 1 to the answer.
Step 2:
Now divide the obtained number by 7. The remainder gives the year code.
Example:
Find the year code for 1979?
Step1:
79/4, Quotient = 19, remainder = 3
79+19+1=99
Step 2:
99/7, remainder = 1.
Therefore, the year code for 1979 is 1.
Day of the date between 1900 to 2099
Having learnt about month code, year code and day. There is a formula that helps us to find the day of any date between 1900 and 2099.
(Year code + Month code + Date)mod 7
mod 7 means finding the remainder after dividing by 7.
Using the above formula we can find the day problem for any given date from the year 1900 to 2099.
Example 1:
Find the day of 21/05/2023?
Answer:
Here year code is 23/4 = 5, Remainder =3.
23+5 = 28
28/7= 4; Remainder = 0.
Therefore, the year code for 2023 is 0.
Month code for May is 0
The formula to find the day is (Year code + Month code + Date)mod 7
(0 + 0 + 23)mod 7 =21/7 = 3; Remainder =0
The day code for 0 is Sunday.
Therefore the day of 21/05/2023 is Sunday
Example 2:
Find the day of 07/04/1979?
Here the year code is :
79/4 = 19, Remainder = 3
79 +19+1 = 99
99/7 = 14; Remainder =1.
Therefore the year code is 1.
Month code for April is 5.
The formula to find the day is (Year code + Month code + Date)mod 7
(1 +5 + 7)mod 7 = 13/7 = 1; Remainder =6.
The day code for 6 is Saturday.
Therefore the day of 07/04/1979 is Saturday.
