There Might Be A Reason Why He Doesn't

From Reader's Digest:

Coworker 1: My son just turned 18 months old.

Coworker 2: So is that like a year and a half old?

Coworker 1: You really aren't sure if 18 months is a year and a half?

Coworker 2: How am I supposed to know that? I don't have kids.