I gave up after beating the hell out of it.

3648 presents a new problem too, it points out that the old machine thought it used daylight time, and the new one doesnt.

 
use Date::Manip;
acycle("2016080100:00:00",'2016123100:00:00');       # it knows im in 
+a daylight zone and comensates 
acycle("2016080100:00:00GMT",'2016123100:00:00GMT'); 
acycle("2016080100:00:00CDT",'2016123100:00:00CST'); 
acycle("2016080100:00:00CST",'2016123100:00:00CST');  # i cant explain
+ this one 
acycle("2016-08-01T00:00:00CST",'2016-12-31T00:00:00CST');  # i cant e
+xplain this one 
acycle("2016-08-01T00:00:00-0500",'2016-12-31T00:00:00-0500');  # but 
+this is ok 

exit; 
sub acycle {
my $dt1=shift;
my $dt2=shift;

my $fe=DateCalc($dt1,$dt2,0); 
my $fse=semi_exact($fe); 
printf "dt1:%25s (%25s) \ndt2:%25s (%25s) \n                  -> %s \n
+"
     ,$dt1,UnixDate($dt1,'%Y-%m-%d-%H:%M:%S%Z')
     ,$dt2,UnixDate($dt2,'%Y-%m-%d-%H:%M:%S%Z')
     ,$fse;
#print 'dt1:'.$dt1.'('.&UnixDate($dt1,'%Y-%m-%d-%H:%M:%S%Z').')'
#    .' dt2:'.$dt2.'('.&UnixDate($dt2,'%Y-%m-%d-%H:%M:%S%Z').')'
#    .' ->'.$fse."\n";
} # acycle 


sub semi_exact { 
  my $delve=shift; 
  my @parts=split(':',$delve); 
  my $h0=$parts[4]+$parts[3]*24+$parts[2]*7*24; 
  my $w=sprintf('%d',$h0/(7*24)); 
  $h0=$h0-$w*7*24;
  if ($w<0) {$h0=$h0*-1;}
  my $d=sprintf('%d',$h0/24); 
  $h0=$h0-$d*24;
  my $delvse="0:0:$w:$d:$h0:$parts[5]:$parts[6]";
  return $delvse; 
} # semi-exact
[download]

dt1:         2016080100:00:00 (   2016-08-01-00:00:00CDT)
dt2:         2016123100:00:00 (   2016-12-31-00:00:00CST)
                  -> 0:0:21:5:1:0:0
dt1:      2016080100:00:00GMT (   2016-08-01-00:00:00GMT)
dt2:      2016123100:00:00GMT (   2016-12-31-00:00:00GMT)
                  -> 0:0:21:5:0:0:0
dt1:      2016080100:00:00CDT (   2016-08-01-00:00:00CDT)
dt2:      2016123100:00:00CST (   2016-12-31-00:00:00CST)
                  -> 0:0:21:5:1:0:0
dt1:      2016080100:00:00CST (   2016-08-01-00:00:00CST)
dt2:      2016123100:00:00CST (   2016-12-31-00:00:00CST)
                  -> 0:0:21:5:14:0:0
dt1:   2016-08-01T00:00:00CST (   2016-08-01-00:00:00CST)
dt2:   2016-12-31T00:00:00CST (   2016-12-31-00:00:00CST)
                  -> 0:0:21:5:14:0:0
dt1: 2016-08-01T00:00:00-0500 (   2016-08-01-00:00:00CDT)
dt2: 2016-12-31T00:00:00-0500 ( 2016-12-31-00:00:00EASST)
                  -> 0:0:21:5:0:0:0
[download]