The way to calculate the date

January has 31 days. Since February has 28 days, it means that every date in February will be three days later than the same date in January. Following the total number of days in every month, here is a list. 

January 0

February 3

March 3

April 6

May 1

June 4

July 6

August 2

September 5

October 0

November 3

December 5

To find the exact day of the week, here are the following steps. For example 1986.2.19

Step 1. Find the number on the list, February is 3

Step 2. Take the date of the month, 19

Step 3. Take the last two digits of the year, 86

Step 4. Find the number of leap years, take the last two digits of the year and divide it by 4. 86/4=21

Step 5. Add the four numbers together. 3+19+86+21=129

Step 6. Number divided by 7, remainder is 3. (Wednesday)