or download this
# create a DateTime object from an ISO timestring
my $isostr = '2021-10-09T11:13:57'; # jd 2459496.96802
my $dt = DateTime::Format::ISO8601->parse_datetime($isostr);
...
my $diff = $end_epoch - $start_epoch;
my $hard_bottom = int($start_epoch);
$logger->info("integer bottom is $hard_bottom");