Dunno where you get that info, a proper hanging breaks the neck and is pretty much instant. You may be referring to "hangings" where the victim is hung up by their neck and chokes to death and that takes longer but not Half an hour.
Although judicial hanging breaks the neck (cervical vertabrae to be exact), death is caused by strangulation whilst the person on the rope is unconscious. The ezact time can vaty. It is for this reason that anyone hanged in the UK was left for 1 hour on the rope.