Time and time again?

I was at a co-worker's place today and his stove/oven's time was an hour off because of Daylight Saving's Time. Now this is something that happens (or will happen!) to all of us eventually - we do something extremely simple, then later we come back to it, and can't figure out how in the world we did it. The same thing happened to me when I had to change my car's clock - one time change I did it without a problem, I looked at the choices and figured it out almost instantly. The next time change, I couldn't figure it out for the life of me.

I just thought I'd note how interesting it is that our minds can figure out something so quickly one moment, and then have so much difficulty with the same problem in the future. This is probably attributed to many factors like mood, environment (place, sounds, people around you), nourishment, etc.