For those who don't know what horary is: it's a type of astrology where you ask a question such as "what is the reason for my marriage failing?" or "which is the right job for me?" and immediately cast a chart of the time and place you asked the question and look your answers in the chart. It's similar to tarot readings, pendulum, rune castings (the way most non-Satanists use them for divination) and other types of divination.
It's the only type of astrology that doesn't depend at all on a natal chart, so you can use it even if you don't know the date or time of birth.