At one my jobs we were required to enter personal data on people. One day while working a co-worker was having difficulty entering the information into the system.
So she asked the girl sitting beside me and myself for help. However when she gave us the birthday, it was for later on in that year, so could not be the correct birth date.
We realized this immediately and said, "You can't enter it, because it hasn't happened yet," in almost perfect stereo.
The girl said thank you, then continued to stare at her computer for a full minute. Then she said. "Oh! I see what you mean now!"
The girl next to me and I looked at each other in wonder. At this point, I slid my chair back and said it was time for my break.
To make things even worse for the girl, there had been a sticker on the page she was entering that noted the problem with the birth date and listed the correct date and was highlighted.
Some days jobs just aren't worth the pain.