Telephone Etiquette

When I was growing up, my parents always said that you should never call anybody after 9 pm. However, it's free for me to call people after 9 pm. This creates an interesting dilemma whenever I think of calling anyone in the evening.

I think the 9 pm rule might be shifting to 10 pm if you are calling from one cell phone to another... but when calling Grandma (and other devoted land-linders), the 9 pm rule still applies!