Which year to use before Georgian calendar?

[jbh001]

Different calendar is almost like different languages.
I think is better to store the original registration and put the conversion rules into notes, for example with numbered month, avoiding misunderstanding to readers.
Change of calendar are known in heaven, no chance to fault.

I agree, although I might do the exact opposite, that is, use a proleptic Gregorian calendar date and then put the actual date in the notes.