How to convert the date in seconds from Christmas Chr. convert to calendar date?

Question

Java

There is a specific date in the format 63672393600, which is in seconds since Christmas.
How to convert it to a calendar date? If all calendars in java come from 01/01/1970?

Answer 1

Calculate how many seconds in a year and divide, we get the number of years, the remainder is months, by analogy with the year, and so on to the desired accuracy

Answer 2

How to convert it to a calendar date

What calendar? And do you consider high-powered ones according to modern standards or not? And a bunch of all sorts of fucking changes in the chronology how to take into account?
I offer a simple solution. Do you know what the date "63672393600" is? Take the same date in unix timestamp (from 01/01/1970), subtract the second from the first. Get a constant offset. And then when you need to translate your date - first subtract the constant offset from it (in fact it will be 01/01/1970 in your format) and then consider it as a regular unix timestamp.