Calculate dates before 1970, in forms etc–Defeat Windows limitations!

In form, designate 3 separate fields for your date.
Mine were cdoby (i.e., ClientDateOfBirthYear), cdobm
(ClientDateOfBirthMonth), and cdobd (ClientDateOfBirthDay).
AGE (or other date calculations): 

<?php
	// BIRTH YEAR NUMBER
				
$yage = "$cdoby";  	// $yage is a string
$yage += 0;   	// $yage is now an integer--year of birth

	// BIRTH MONTH NUMBER

$mage = "$cdobm";  // $mage is string
$mage += 0;   	// $mage is now an integer--month of birth

	// BIRTH DAY NUMBER

$dage = "$cdobd";  // $dage is string
$dage += 0;   	// $dage is now an integer--day of birth
				

	//CALCULATE AGE
	//(including consideration for leap years)

$leap = date("L");  //adds 0 if not leap year, +1 if it is			
$nowday = date("d");	//day part of today's date
$nowday += 0;	// convert date string to true integer

$lnowday = ($nowday + $leap); //leapyear consideration
$nowmonth =date("m");	//month part of today's date
$nowmonth += 0;	// convert date string to true integer
$myyear = date("Y"); 	//this year as 4 digit number		

$age = ($myyear-$yage);  //Almost there!

?>
	//DETERMINE IF BIRTHDAY HAS TAKEN PLACE OR NOT
	//AND PRINT AGE
<?php
if (($nowmonth < $mage) OR (($nowmonth < $mage) AND ($lnowday < $dage))) {
   $age=$age-1;
}

print $age

?>

It works great--however, I've only tested it back to the year 1949.

You folks have helped me so much--I hope this benefits someone as well!