How do i know that there is 13 prime dates in September?

In September, the prime dates correspond to the days of the month that are prime numbers. The prime numbers between 1 and 30 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, and 31. In September, the prime dates are 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29, totaling 10 prime dates. Therefore, there are actually 10 prime dates in September, not 13.