You can add days, weeks, months, and years to a known date to determine a future date. For example, if you have a minor's birth date and you want to determine when the minor will turn 18 years old, you can simply add 18 years to the birth date.
The following computations show how to add days, weeks, months, and years to a Date variable.
You can also subtract days, weeks, months, and years from a date by replacing + with - in the script.