( int month, int day, int year )
Valid Range for Gregorian Calendar 4714 B.C. to 9999 A.D.
Although this function can handle dates all the way back to 4714
B.C., such use may not be meaningful. The Gregorian calendar was
not instituted until October 15, 1582 (or October 5, 1582 in the
Julian calendar). Some countries did not accept it until much
later. For example, Britain converted in 1752, The USSR in 1918
and Greece in 1923. Most European countries used the Julian
calendar prior to the Gregorian.
Example 1. Calendar functions
$jd = GregorianToJD(10, 11, 1970);
$gregorian = JDToGregorian($jd);