Lesson: 01 | Calculating Age from Birthdate

This formula is likely used to calculate a person's age based on their birthdate. The expression uses several functions:

1. ISBLANK checks if the value in the "PersonBirthdate" field is empty.
2. NOT reverses the value of the ISBLANK function, so that the expression will only proceed if the "PersonBirthdate" field has a value.
3. DATE creates a date from separate year, month, and day values.
4. MONTH extracts the month value from a date.
5. DAY extracts the day value from a date.
6. TODAY returns the current date.
7. YEAR extracts the year value from a date.

The expression uses these functions to compare the birthdate to the current date and determine the difference in years. If the birth month and day have passed, the difference is simply the number of full years between the birthdate and today. If the birth month and day have not yet passed, the difference is one less year. If the "PersonBirthdate" field is blank, the expression returns "null".