Biological Clock
Some times you wake up in the night and without looking at the clock you san say what is the time. This is a biological clock mechanism that works in us all the time. It is there to remind us when to eat and when to sleep. The jet lag that is reported by long distance fliers over different time zones is due to this. The place where he has landed would show a time of 1 pm but his biological clock would not have got adjusted and would be making the body feel like it is 1 am in the morning. With a little rest the biological clock adjusts to the new situation and this is no cause for worry.