by Opera di Santa Croce
Thanks for the answer! It looks like it's really a complex question.... I look forward to know more when it's more convenient for you (and I am sure I am not the only one who got curious after hearing De Micheli here!:
Hi @aresgames, you always ask the toughest questions! You can see that you're really very interested in history :).
The difference in dates between the Gregorian and Julian calendar is relatively minimal, what really made the difference between the 15th century and now is that in Florence, the new year started on March 25. But this only creates difficulty in records that regard the first three months of the year, and normally when we cite historic dates we specify "new time".
There is a short publication in our archive that was made available after the restoration of this fresco, and that explains it better. We'd have to dig it out to be able to give you a better explanation of how they calculated that date based on the star signs and exactly what calendar it corresponds to - and even then, this is expert astrology, so a bit beyond us!
And another question on that date... It's July, 4th according to OUR calendar, or the Julian calendar that was used at that time?
Is there any conjecture about the "mistery date" of July 4th, 1442? A wedding? A date of birth or date? Is there anywhere to look for more details?