Convert epoch difference to number of days

Question

I computed the difference of two ISO 8601 dates after coverting them to epoch. How can I get the difference of them in number of days? My code is

my $ResolvedDate = "2014-06-04T10:48:07.124Z";
my $currentDate = "2014-06-04T06:03:36-04:00"

my $resolved_epoch = &convert_time_epoch($ResolvedDate);
my $current_epoch = &convert_time_epoch($currentDate);

if (($resolvedDate - $currentDate) > $noOfDays) {
    print "Difference in greater than x\n";
    $built = 0;
    return ($built);
} else {
    print "Difference in smaller than x \n";
    $built = 1;
    return ($built);
}

sub convert_time_epoch {
    my $time_c = str2time(@_);
    my @time_l = localtime($time_c);
    my $epoch = strftime("%s", @time_l);

    return($epoch);
}

Here in addition to $built I also want to return exact number of days, Resolved date is greater than Current date.

Answer 1

"number of days" is awkward, because this is localtime and DST exists (or at least, may exist).

By simply dividing by 86400 you can easily obtain the number of 24-hour periods, which may be sufficient for your purposes.

If you want the true number of times that the mday field has changed, this may be slightly different from the value obtained by this simple division, however.

Answer 2

If the dates are in epoch seconds, take the difference and divide it by the number of seconds in a day (which is 86400). Like so:

my $days_difference = int(($time1 - $time2) / 86400);

If you use DateTime then

my $duration = $dt1->delta_days($dt2); #$dt1 and $dt2 are DateTime objects.
print $duration->days;