I'll say I have no idea how wiki "messaging works" first off, and secondly that I'm not hung up about this (though I felt you got agitated by my misunderstanding) and rather I'm wondering something.
If Gensokyo celebrates New Years using an old calendar... why do they... NOT do that, basically? I refer to times when New Years is celebrated within the canon, for example chapter 15 of Strange and Bright Nature Deity.
The months are roughly 1:1 right? About a 20 day or 2 week difference or something. Well, in that 15th chapter which takes pace in December and around New Years in the real world... well, everyone celebrates New Years: the fairies, Marisa and Reimu, and the residents of SDM. My curiosity is thus: I am honestly wondering how old that calendar stuff is and how exactly it's adhered to. It seems like "not very closely".