doing math

OK.  Work this through with me:

Most movies shoot at about 20-30 frames per second (fps).  Let's go with 24fps as a nice easy number to work with.
I'd like to make a 60 second time lapse movie of our Solstice Party tomorrow.
24fps x 60 seconds = 1440 frames.

There is 60 seconds in one minute.
3600 seconds in one hour.

We should figure on about six hours of party time.
Six hours = 21600 seconds
21600 seconds / 1440fps = a photo taken every 15 seconds.

With me so far?

I have a little Logitech web cam and Photojoj tells me that Microsoft’s PowerToys has a webcam timershot program I can download for free.  I have a nice vantage point high up in the room to take shots from. 

So the question comes down to this:

HOW DID I HIT A CAR ON WEDNESDAY? 

Dammit.  I was trying so hard to be careful.  It was a narrow street and I was concentrating on NOT hitting the car coming in the opposite direction when I rubbed into another car parked on the corner in the red zone.  No damage was done to either car and they were parked somewhere they shouldn't have been, but I still feel like an idiot.  Especially when you consider there was a woman sitting in the passenger seat of the car NURSING HER BABY.  So tell me.  How'd all that happen when I can so clearly think things through and DO MATH?  Shouldn't I be immune to that kind of idiocy by now?