I once saw a movie on the TV sometime in the 1990s. I don't remember a whole lot (maybe I didn't even see the whole movie), only one particular scene, which made quite an impression on my young self, and it still pops into my mind from time to time.
So, there was a book in it, a very old magical (?) book, which, if used correctly, revealed the happenings of any specific day in history: when opening it with a specific date in mind, handwriting appeared (fade-in) on the yellowish page, listing all the events of that day. And the main guy (young-ish, but maybe bespectacled? lean guy) and his Watson/sidekick (who was maybe a woman?) used the power of this book to solve a mystery of some kind. The plot twist was, the book showed nothing about a specific date: it just showed a blank page, and the characters thought this incredulous. I distinctly remember the guy saying something along the lines of "but it's impossible that nobody died or was born on that day!", and this kind of stalled the investigation (they even thought the book got broke), until these clever guys realised that the date was one of the missing days of the Gregorian calendar change, between 4 October 1582 and 15 October 1582. Or maybe it was about the introduction in America, 2 September 1751-14 September 1751, I'm not really sure.
And the guy said: "11 October 1582 never existed!", then went on to explain the Gregorian calendar reform, and realised the date they got was bogus.
Oh boy, this fascinated me so much.
Anyway, this is all I remember. Oh, except, there's this other thing that it was really dark (candlelight, maybe?) when they were handling the book - now that I think about it, I recall that the book needed a ritual to function.
There's a chance I didn't even see the whole movie, just these couple of scenes.
It didn't really seem like an A-list production, maybe it was a TV movie, or actually, it might have been a series. This was in Hungary, but I'm almost certain it wasn't a Hungarian production. I think it had a late 80s/90s feel to it in terms of fashion and hairstyle. I think it was all a fairly light-hearted, family-oriented thing.