Alright, great, soonix, thank you. I can dispense with that longer script and focus on the essential output and simply glean the values. Your formula looks right to me, and I'll test it as best I can. I have to wonder out loud how you were able to cobble it together from scratch so quickly. (I've been puzzling for weeks.) Julian dates aren't the stuff that most people can wrap their heads around. Let's look at a toy script:

#! /usr/bin/perl
use warnings;
use strict;
use 5.010;
use DateTime;
use DateTime::TimeZone;

my $begin = 2457205.09272861;
my $middle = 2457205.09613609;
my $end = 2457205.09954643;

my $dt1 = jd2dt($begin);
say "date1 is $dt1";
my $dt2 = jd2dt($middle);
say "date2 is $dt2";
my $dt3 = jd2dt($end);
say "date3 is $dt3";
my $dur = $dt3-$dt1;
say "dur is $dur";


sub jd2dt {
    # convert JD to DateTime
    my $jd_to_convert = shift;
    my $days = int $jd_to_convert;
    # that odd date is "julian day zero", converted to "proleptic" gre
+gorian calendar
    my $dt = DateTime->new(year => -4713, month => 11, day =>24, hour 
+=> 12, time_zone => DateTime::TimeZone->new( name => 'UTC' ))->add(da
+ys => $days);
    $dt->add(hours => 24 * ($jd_to_convert - $days));
    say "date is $dt";
}

[download]

Output:

date is 2015-07-01T14:13:31
date1 is 1
date is 2015-07-01T14:18:26
date2 is 1
date is 2015-07-01T14:23:20
date3 is 1
dur is 0

[download]

How is $dt unity at the end of the subroutine and a well-formed string in main?

How do I fix my duration calculation to reflect the difference in two dates?

Thanks again for giving my starwatching a perl infusion.

In reply to Re^2: getting a utc value from julian date by Aldebaran
in thread getting a utc value from julian date by Aldebaran

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