seems to be the number of days since January 1900.
January 1900 + 23012 days = 1th January 1963
One way to get 23012 from 1.1.1963 would be to calculate 1th Januar 1963 minus 1th January 1900 = 23012 days.
I'm not sure if we have a ready-made function for this calculation in Mp3tag.
The calculation of the days seems not that easy:
-
Calculate the Years
From January 1, 1900, to January 1, 1963, there are 63 years.
Each normal year has 365 days, so: 63 × 365 = 22995 days -
Account for Leap Years
Between 1900 and 1963, there were 16 leap years (every year divisible by 4, except 1900, which was not a leap year).
Each leap year adds one extra day, so: 16 × 1 = 16 days -
Total Number of Days
22995 days (regular years) + 16 days (leap years) = 23011 days
Adding 1 day for January 1, 1963, results in 23012 days.
Formula:
Calculation example with 1963:
((1963 - 1900) × 365) + ((1963 - 1900)/4) + 1 = 23012
or
(63 x 365) + (63/4) + 1 = 23012
or
22995 + 16 + 1 = 23012
It gets even more complicated if you want to calculate the difference between 1.5.1963 and 1.1.1900 because you need to calculate the days in the year 1963 and check if it is a leap year. In 1963 these would lead to + 120 days. But for the 1.5.1964 it would be + 121 days because February would have 29 days...
Maybe someone sees an easier way to create a formula than this approach?