John wasn't sure she had an appointment , or was even in her office , but he found himself in front of the door at 1700 . For the life of him , he couldn't remember what time the concert was tonight . He hoped it wasn't too soon ... He had told Colleen that he would be late tonight and that he probably would step in , get something to eat , and then go back to the shuttle bay . She had said she would probably join him at some point , and leave Keith with Saril . 
Question: What's a possible reason John couldn't remember what time the concert was ?
Because John is forgetful .