Electronic age verification devices take the math out of checking ID. Just swipe the customer's driver's license and the machine does the rest.
Sounds simple.
We Card calendars take the math out checking ID too. For every day of the month, the calendar provides the birth date required for a legal tobacco sale. In other words, if it's Dec. 19, 2009 and the legal age for buying tobacco is 18, then the customer must have a birth date of Dec. 19, 1991 -- or earlier.