Annual profection
Annual profection advances the Ascendant one whole sign for each year of life, so the house it reaches names the year's theme and its ruler becomes the lord of the year.
The arithmetic is deliberately simple: age modulo twelve gives the house, counting the first house as age zero. At twelve, twenty-four and thirty-six the profection returns to the first house, which is why those ages recur in Hellenistic accounts of life stages.
The lord of the year is the technique's real output. Wherever that planet sits, and whatever transits reach it, is where the year's attention goes. It is a way of deciding which transits matter, not a forecast in itself.
Frequently asked
How do I find my profected house?
Divide your age by twelve and take the remainder, then count that many houses from the first. Age zero is the first house.
What does the lord of the year do?
It marks which planet the year runs through, so transits touching it are read as the year's significant ones.