First of all, the answer to this question is not unique. "A summer vacation" basically defaults to July and August. A month, maybe four weeks, maybe five weeks (for example, 1, then 8, 15, 22, 29). There are at least four (such as the 7th, 14, 2 1, 28), but it is definitely impossible for two consecutive months and two consecutive Thursdays. So the answer is eight or nine times.