Period

A kindergarten class had a homework assignment to find out about something exciting and
relate it to the class the next day. When the time came to present what they' d found, the first
little boy walked up to the font of the class made a small white dot on the blackboard and
sat back down, Puzzled, the teacher asked him just what it was,
It' s a period," said the little boy.
Well, I can see that," she said, "but what is so exciting about a period?"
Damned if I know," said the little boy, "but this morning my sister was missing one, Daddy
had a heart attack, Mommy fainted, and the man nest door shot himself."