Is it just me, or would "I write it on my calendar" sound more natural?
Actually I would use both. I would write it ON my calender if it was a calender hanging on the wall. I would write it IN my calender if it was a little pocket calender or the one on my phone.
Except I'm struggling to find a scenario where I would use this form of the present tense... Either I'd say "I'll write it" or "I'm writing it". Neither seems to be accepted by Duo...
It's not just you; it's most of the English-speaking world.
"I write it on my calendar." is also accepted by Duolingo. At least it is now if it wasn't before.
I write it down in my calender? What's wrong with that one?
Apparently nothing, though to me it feels wrong. To me a calendar is a thing you hang on the wall, a surface, that you write on. Not a book-like thing like an agenda, that you write in. But that's my faulty brain, alright:p
Yeah, I think that's our Dutch interpretation. As far as I know, the word "calendar" can be used for both our "kalender" and "agenda" in English.
But what about those big desk to-do calendars?
I agree with those above, in English we write ON a calendar and IN a diary.