Multiple choice If the first day of the month is a Sunday, what special day happens in that month? 2 full moons lunar eclipse Friday the 13th month will have 30 days Reveal answer Fill a bubble to check yourself C Correct answer Explanation If the 1st of a month falls on a Sunday, counting forward by adding 12 days brings you to the 13th day of the month, which must be a Friday. This mathematical pattern ensures that any month starting on a Sunday will always have a Friday the 13th.