0504 If statement (judgment date)

Case LIST:

First, judge the day of the month

Ideas: 1, first judge whether the year is correct (1<= year <=9999)

2. If the year is entered correctly, determine if the month is correct (1<= month <=9999)

3, if the month input is correct, then the judgment Day is correct

4, the day is divided into three kinds of situations

①1,3,5,7,8,10,12 these months are 31 days

②4,6,9,11 these months are 30 days

③ February There are two different cases, the leap year is 29 days, common year is 28 days

0504 If statement (judgment date)