Master numbers (11, 22 and 33) can be a curse and they can be a blessing when they appear in a Numerology chart -- but above all, they can be confusing! The rules for when to reduce Master numbers to single digits and when to leave them as double-digit numbers are not as easily defined as we would like them to be.
When a double-digit number or a date does not have the power to unleash Master number potential, we reduce it to a single digit. For example, the month of November is an 11 and, in theory, might be considered a Master number. However, a month simply does not have Master number power. If it did, we would be going through some considerable turmoil every year come November. Similarly, days by themselves do not have Master number energy either. Consequently, we reduce the 11th and 22nd days of any month to 2 and 4, respectively, during almost all calculations. An exception to that rule is when we calculate the Life Path and Birth Day numbers -- in part because they are core numbers in a chart, but also because they are more static, as opposed to the dynamic, changing nature of cycles. Keep in mind that the date of your birth is a dynamic number when viewed as just a date within the Universal cycle of calendar years, but it is a static number when seen as a single moment, a window in time through which you stepped into this life; the momentous event that is your birth.
When adding the digits found in a date to calculate cycles, such as Personal Year, Month and Day cycles, we always reduce the Master numbers, both within the date itself and in the process of adding them. Therefore, 9/11/2001 is first reduced to 9-2-3 (reduce 11 to 2, and 2001 to 3). As I mentioned, a date by itself does not have Master number potential.
If, however, we want to analyze a particular date, pulling it out of the context of a cycle, we still work with units that have been reduced to single digits, but now we recognize and acknowledge Master numbers during the process of calculation. Hence the fact that 9-2-3 (for September 11, 2001) has a First Pinnacle of 11 (from 9 + 2).
This is an apparent contradiction, but it does make some sense when you think about cycles as having progressive momentum, while a precise date is a specific point on that linear progression -- dynamic versus static.
To continue our little venture into confusionism, when adding digits to find a sum total in almost all calculations based on a name, we do not reduce Master numbers at any point. Even when we look for cycles that are derived from the name, such as Transit and Essence cycles, we do not reduce Master numbers. To make it even more mystifying, in the case of Essence cycles, we pay as much attention to the double-digit numbers as we do to their single-digit sums, even when those double-digit numbers are not Master numbers.
Finally, some letters, just like dates, have Master numbers. The K is the 11th number and the V is the 22nd number, two Master numbers that have been reduced to 2 and 4 respectively because Numerologists do not assign Master number powers to letters. They do, however, assign Master number power to additions that result in 11 or 22. Basically, the logic that decides on the fate of Master numbers when working with dates mirrors the logic used in the process of analyzing names.