Babysitting?

It was another babysitting night
I was supposed to go over at eight
I locked my door and then turned out the light
I even left early to not be late

I drove across town to get to their house
and then I made the turn onto their street
then I parked my car and I checked my blouse
opened the car door and came to my feet

I walked to the door and I rang the bell
and the three year old did answer the door
he looked quite confused and his mom as well
his sister's face showed a look of horror

I soon found out as his mother did speak
I had, in fact, showed up on the wrong week!