#!/usr/bin/perl -w
require 5.003;
use  POSIX "floor";

@DoW = ('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
@MoY=('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
# For a leap year February needs to be corrected (done in Step 1).
@MonthLength = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

# ------------------ get input ---------------------
print "\n Give me a date and I'll tell you the day of the week.
\n\tMonth?  [1,...12]   ";
$Month = <STDIN>;
chomp($Month);
print "\t\t (you picked  $MoY[$Month-1])\n";

print "\n\tDay?  ";
$Day = <STDIN>;
chomp($Day);

print "\n\tYear? [as: 2012]   ";
$Year = <STDIN>;
chomp($Year);

# --------- main program begins here ----------------
if  ( (($Year % 4) == 0) and
    ( (($Year % 100) != 0) or ( ($Year % 400) == 0) ) ) { $MonthLength[1]=29; }

$Day_Num = 0;		# Initialize
for  ($i=0; $i < ($Month-1); $i++) {	# Days in preceding months
    $Day_Num = $Day_Num +  $MonthLength[$i];
}
$Day_Num = $Day_Num + $Day;            # Add correction for current month.

$Y1 = $Year - 1;           # previous year
$Day_of_Week = ($Day_Num + $Y1 + floor($Y1/4) - floor($Y1/100) + floor($Y1/400) ) % 7;

$Answer = $DoW[$Day_of_Week];
print "\n==> $MoY[$Month-1] $Day, $Year is a $Answer\n\n";