[theK]

Its probably way too late to implement something like this but the idea is still a good one.

Thinking of it, wasn't there a "metric" calendar or something that sort of did this?

[Nzen]

The French Republican Calendar had five/six complementary days [0] at the end of the year that were part of no particular month. They were, however, spent contiguously between summer and fall, rather than between each season.

[0] https://en.wikipedia.org/wiki/French_Republican_calendar#Com...