$ perl -Mwarnings -Mstrict -ML -E'
my $parser = DateTime::Format::Strptime->new(pattern => "%Y%m%d%H:%M:%S", on_error => "croak");
my $dt1 = $parser->parse_datetime("2016080100:00:00");
my $dt2 = $parser->parse_datetime("2016123100:00:00");
say $dt2->delta_days( $dt1 )->in_units("days");
'