AgeYMD :: An accurate age calculator

This function, written with the help of Doug Steele MVP, is very similar to Diff2Dates function, but is solely intended to accurately calculate a person's age, given their birthdate and a reference date. It can calculate the person's age and display the result as words. For example:

7 years 6 months 5 weeks 4 days 3 hours 2 minutes 1 second

You can specify which (or which combination) of the cumulative periods to return. For example:

7 years 29 weeks 4 days 3 hours 121 seconds