In computer-speak, labels have to be single letters or single words, which disqualifies my birthday.

Can you think of a valid label?

my_birthday1/1your birthday1970

Sweet! Labels don't have to be real words and can include numbers, as long as they don't start with them. Also, it's smart to use meaningful labels.

Are you sure? While labels don't have to be real words and can include numbers, they can't be numbers or have spaces.