The "lord of the year" that changes every year, and the big life cycles that come round every several years.
The Solar Return doesn't look only at one year's sky. It also reads the profection that turns with your age and the big cycles in which slow planets come back to their birth positions.
Profection: the lord of the year
Annual profection
A classical technique that moves one house per year of age to read the year's main theme. The planet ruling the sign of that year's house is called the lord of the year.
The year you're born (age 0) is the 1st house, age 1 the 2nd, age 2 the 3rd, moving one house a year. At 12 you're back at the 1st house. The traditional ruler of that year's house sign is the lord of the year.
Example: with a Leo Ascendant at age 30, 30 divided by 12 leaves 6, so the 7th house (Aquarius) is active. Saturn, the traditional ruler of Aquarius, is the lord of the year.
The big life cycles
When a slow planet returns to its birth position or stands opposite it, it's read as a change of season in life. The Solar Return tells you when one of these comes within 3° during that birthday year.
Jupiter return
When Jupiter comes back to its birth position. It happens about every 12 years, around ages 12, 24, 36 and 48. It's read as the start of a new cycle of growth, with wider horizons and opportunities.
Saturn return
When Saturn comes back to its birth position. It happens about every 29–30 years, around ages 29–30 and 58–60. It's read as a time to reset responsibilities and firm up the structure of your life.
Saturn opposition
When Saturn stands opposite (180°) its birth position, at the midpoint of the Saturn cycle, around ages 14–15 and 44. It's read as a time to review what you've built so far.
Uranus opposition
When Uranus stands opposite its birth position. It comes once, around age 40, and is often called the midlife turning point. The urge for postponed change and for freedom grows.
Nodal return
When the lunar nodes come back to their birth position, about every 18.6 years, around ages 19, 37 and 56. Halfway between, about 9 years later, comes the nodal opposition, when the nodes are reversed. It's read as a time to choose your direction again.
The exact ages vary a little from person to person. When a planet goes retrograde, it can pass through the same cycle two or three times.