It is culture-specific, but if we're considering the western world as a culture then it's essentially the right answer.
Only one of my clients maintains operations outside of Europe and America, and they're not working during the winter period. Regardless, the vast majority of western users on this forum need only care about the western market.
While true, this only matters to B2B operations. As a customer I am less likely to visit a health website because I'll be spending Christmas with my family.