Because 30 divided by 7 equals 4, there is 2 left.

It can be seen that there are more than four weeks and two days in June (emphasis: except that the remainder is an inexhaustible number in the future, the center of gravity is redundant)

If there are five Sundays in June, Sunday is an extra day, and the other extra day is either Saturday or Monday.

So we assume that June 1 day and June 2 are redundant days (the remaining 28 days are exactly 4 weeks).

If there are more Saturdays and Sundays, then June 1 day is Saturday; If it is more than Sunday and Monday, then June 1 day is Sunday.

(key: classified discussion, exhausted possibilities, there are two answers! )