Because of this, the appearance of a certain day name follows a constant mathematical formula. This subroutine/utility has had that mathematical formula written into it along with the dynamic generation of certain constants which will affect the outcome. (i.e. leap years).

The subroutine calculates Leap Years on it's own and makes all necessary adjustments for them.

To use this subroutine you must pass three arguments and there are a few rules about these arguments. The three arguments, in order are the Year, the Month and the Day of the Month for which you want to return a day's name.

Here are the rules for the arguments being passed:

1. The arguments must all be DIGITS. You can not pass, for example, the word 'August'.
2. The year argument MUST be four digits long.
   i.e.: 1998 is valid, 98 is not valid.
3. The year argument must be equal to or greater than 1800 and less than or equal to 2099.
4. The subroutine will check to ensure that the day of month submitted does not exceed the permitted number of days in that month. For example, submitting 31 as the day of the month is valid for July but it is NOT valid for June.

If you violate any of these above rules the subroutine will return a null value (zero). If you successfully pass the above arguments, then the subroutine will return the name of the day corresponding to the day of month, month and year submitted.

Here are some examples of calls to the subroutine:

EX.1

$year = 1965;
$month = 6;
$day = 19;
$name_of_day = dayname($year, $month, $day);

EX.2

$name_of_day = dayname(1965, 6, 19);

EX.3

$year = 1965;
push(@date_arguments, $year);
$month = 6;
push(@date_arguments, $month);
$day = 19;
push(@date_arguments, $day);
$name_of_day = dayname(@date_arguments);

EX.4

$month = 6;
$day = 19;
$name_of_day = dayname(1965, $month, $day);

if(dayname($year, $month, $day)) {

	YOUR LOGICAL BLOCK HERE. THIS LOGICAL
	BLOCK WILL EXECUTE IF THE DATE SUBMITTED
	IS A VALID DATE.

} else {

	YOUR ERROR TRAP HERE. IT WILL EXECUTE
	IF THE DAY SUBMITTED IS TOO BIG FOR THE
	MONTH SUBMITTED or a violation of any of
	the other argument rules.

}

To use this subroutine either cut and paste it into your own script or simply require this script anywhere before you first call the subroutine by simply placing the following line in your script (without the hash mark of course):

require 'dayname.pl';