Usecase is that there are various embedded/industrial/enterprise systems that return and expect dates in either of those two formats as part of their API. Eithe

Usecase is that there are various embedded/industrial/enterprise systems that return and expect dates in either of those two formats as part of their API. Either because they want to represent the idea of "month" or because they don't care about days and not about week days and months (Implementing whole calendar in random embedded/industrial system is unnecessary busywork that costs you not only effort but also code size)