"Time, the mexican way" joke

A tourist is walking down an alley in Mexico. Wanting to know
the time, he walks up to a mexican who is sitting on the ground
next to a donkey. "Do you know what time it is." asks the
tourist.

The mexican raises his arm, lifts up the donkeys' balls
and says, "It's about two thirty".

A little confused, The man
continues on his way. A little while later the tourist returns,
with the same question.

The mexican again raises his arm, lifts up the donkeys' balls and says "It's about five twenty".

Astonished, the tourist can't help but ask how he did it.

Themexican again raises his arm, lifts up the donkeys' balls and
points, "Do you see that clock over there....?".