(12C) Gregorian Date to Julian Day Number and vice versa

[Dieter]

(01-16-2019 05:13 PM)Albert Chan Wrote:  From HP-12C owner's manual, valid date range = Oct 15, 1582 to Nov 25, 4046

It is trivial to extend the range, using the fact Gregorian calendar cycle of 400 years.

I wonder why the date range is limited to this 900.000 day period at all. The usual formula does not cause such limitations.

(01-16-2019 05:13 PM)Albert Chan Wrote:  CJDN(Dec 31, 9999)
= CJDN(Dec 31, 1999) + 8000 years
= (2451545-1) + 8000 * 365.2425
= 5373484

This is also the result with "the usual formula". The WP34s, for instance, handles this easily.

(01-16-2019 05:13 PM)Albert Chan Wrote:  Since 146097 % 7 = 0

I assume you mean 146097 mod 7 here.#-)

But then... who cares about dates in 4000 or 8000 years? The Julian calendar was in use for about 1600 years (but it still is, here and there), and the current Gregorian system is not moch more than 400 years old. So who knows what calendar will be in use several thousand years from now?

Dieter