I suppose the Georgian calendar includes this gap officially? Or did the catholic world just jump from system to system? If it includes the gap officially, then yea, error is the right thing. But if we just moved to a new calendar, then arguably there should be no error. both calendars work for all dates continuously, and we could have conversion functions etc. The gap is just a big flag day (week.)
imo, if i am using Georgian i want that system even retroactively, just like projecting a date back into the stone age. I don't care that a particular geography or culture changed calendars.
So I suppose what is really going on is that some libraries are using Georgian consistently, and others are using some hybrid "civic" calendar that tracks what the romans and the catholics were using, so dates in history books make sense.
The proper name for the calendar using the Gregorian system before the start of the Gregorian calendar is "the proleptic Gregorian calendar".
Think it depends on usage? Taking October 1st and 20th, and you want to know how many days passed, what's the right answer? If it's days lived, you would want the answer to not be 20, as some of those days didn't happen. But in some other context (perhaps something transitioning to the calendar earlier), they did?
Contracts and other similar types of financial instruments existed by this time there must be some way they handled it because something that said that it happened on a date that never occurred - sounds like what lawyers live for.
I’ll draft a Dubia so that when future popes change the calendar they will include a representative code sample and details about how we handle this.
(It’s important to remember that the pope and friends were operating much more like an international standards body than a religious leader when doing things like this.)