Comment by alkonaut

I'd like to add some more constraints, like "I'd like to maximize my time off around christmas", where you can see different alternatives e.g.

using 3 days off, you get 7 consecutive days using 4 days off, you get 9 consecutive days

Because sprinkling them to maximize the total number of days isn't really interesting in reality, even though it's an interesting programming challenge. The reason is that I want to have at least maybe 4 out of 6 weeks off consecutively in the summer months, even if that's not maximizing the total number of consecutive days off. It's those remaining 5-10 days I'd like to optimize for particular holidays and so on.

You could also imagine assigning weights to the months. E.g. 1 day off in July is the same value as 10 days off in January (Say you live where the sun doesn't rise without saying you live where the sun doesn't rise)