#!/usr/bin/env perl
use utf8;
###############################################################################
# This program computes the Julian Day Number of a date.
# 
# Copyright © 2020 Richard Lesh.  All rights reserved.
###############################################################################

use Utils;
use strict;
use warnings;

###############################################################################
# This function computes the Julian Day Number or number of
# days since November 24, -2413 in the proleptic Gregorian calendar.
# Source: https://en.wikipedia.org/wiki/Julian_day#Converting_Gregorian_calendar_date_to_Julian_Day_Number
###############################################################################
sub julian_day_number {
    my ($M, $D, $Y) = @_;
    my $JDN = int((1461 * ($Y + 4800 + int(($M - 14) / 12))) / 4) + int((367 * ($M - 2 - 12 * (int(($M - 14) / 12)))) / 12) - int((3 * (int(($Y + 4900 + int(($M - 14) / 12)) / 100))) / 4) + $D - 32075;
    return $JDN;
}

MAIN:
{
    my $month = 0;
    my $day = 0;
    my $year = 0;
    if (scalar(@ARGV) == 3) {
        $month = Utils::stoiWithDefault($ARGV[0], 0);
        $day = Utils::stoiWithDefault($ARGV[1], 0);
        $year = Utils::stoiWithDefault($ARGV[2], 0);
    } else {
        print Utils::messageFormat("Syntax: \{0:s\} month day year", "JulianDay"), "\n";
        exit 1;
    }

    my $jdn = julian_day_number($month, $day, $year);
    print Utils::messageFormat("\{0:d\}/\{1:d\}/\{2:d\} = \{3:d\} Julian", $month, $day, $year, $jdn), "\n";
}