There are two important long-term cycles in Numerology, each affecting us in a slightly different way: the Pinnacle cycles and the Period cycles. Both are very simple to calculate.
The Period cycles require no calculation whatsoever, other than reducing the units of your date of birth to single digits or, in some cases, Master numbers. Let's use the example birth date of May 15, 1949.
The First Period cycle is the month of birth reduced to a single digit (unless you were born in November, in which case you would leave it as 11 since it is a Master number). In our example, the First Period cycle would be 5, for the month of May.
The Second Period cycle is the day of birth reduced to a single digit. In this case 15 reduces to 6 (because 1 + 5 = 6). If you were born on the 11th or the 22nd, you don't reduce your day of birth, because they are Master numbers.
The Third Period cycle is your year of birth reduced to a single digit. In the case of our example, 1 + 9 + 4 + 9 = 23, and 2 + 3 = 5, so the Third Period cycle is 5.
Each of your Period cycles covers approximately 30 years of your life (this varies based on Life Path numbers, more about that some other time), and can be seen as stages of growth.
The Pinnacle cycles are seen more as an indication of the kind of opportunities, circumstances and environment you will encounter during certain times of your life, and are calculated by adding your Period cycle numbers in four different ways. The sum of your First and Second Period cycle produces your First Pinnacle. This strange concept deserves some contemplation.