When Nathan turns two

Bob went shopping with Colin before Nathan's birthday party. Somehow they got on the topic of how old Nathan is. So when they came home Bob told me about the conversation, it went something like this.

"How old is Nathan?"
"One and a half"
"When does Nathan turn 2?"
"At 5:00."

By the way, the party started at 5:00pm. I guess you don't turn 2 until the party starts. If only that was the way to stop turning 40, just don't have a party!