On the street, a drunk walks up to another person and asks, “What time is it?” 

The person says, “It’s 10 o’clock.” 

The drunk says, “I must be going crazy.  All day long I keep getting different answers.”

What's So Funny?

The drunk keeps getting different answers to his question because he keeps asking at different times of the day.

The reality of the above joke is seen in the truth of the following observation:  Even a broken clock is right twice a day.