my $Y = $C . (join "", @bits[ 1,2]);  ... $Y-1900,

Well, that seems wrong, if $Y is first 3 chars, just get it that way , no need for append/add/subtract..

Also,

1130508154533613 = 2013-05-08 15:45:33.613
c:20 y:2013 M:05 D:08 h:15 m:45 s:33
Wed May  8 15:45:33 2013
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If your year isn't 4 digits, are you sure your month is off-by-one?

I get

#!/usr/bin/perl --
use strict; use warnings;
Fudge('1130508154533613');
sub Fudge {
    use POSIX();
    my( $Y , $M, $D, $h, $m, $s , $ms ) = $_[-1] =~ m{^(.{3})(..)(..)(
+..)(..)(..)(...)$};
  
    my $epoch = POSIX::mktime( $s, $m, $h, $D, $M, $Y, -1, -1, -1  );
    print "$epoch = ",
        POSIX::strftime('%Y-%m-%d %H:%M:%S', $s, $m, $h, $D, $M, $Y, -
+1, -1, -1  ),
        ".$ms" , $/;
    print scalar localtime $epoch;
    print $/;
}
__END__
1370731533 = 2013-06-08 15:45:33.613
Sat Jun  8 15:45:33 2013
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