If an XLSX cell formatted as a Date and its value is '27/07/1016' (UK date style), the value read by openpyxl is '02/08/1016'. Why 6 days are added to the original value?
I have tried several dates, for example:
03/10/1582 will be read as
13/10/1582 by openpyxl and
06/10/1582 will be
But unfortunately, they are wrong.
03/10/1582 should still be
03/10/1582. There is no date from 05/10/1582 to 14/10/1582 in history, due to the Gregorian calendar replacing the Julian calendar in that year.
The dates after '15/10/1582' are correctly processed.
It seems the
datetime module of Python has some facilities to calculate the missing dates between the different calendars, although I think the algorithm itself is problematic.
But in openpyxl, the original cell values should be kept instead of changing them.