I suppose this may possibly lengthen your process time considerably? But am sure if it's a situation you can't help personal or not example, travel due to family emergencies, CIC should be able to reschedule. I say, call them and find out.
The test day is just as important as the oath day so, if you can help it, try not to reschedule. Good luck my friend.
BTW, am not a senior member but felt the need to reply to your post.
Yes, it is possible. You need to call CIC ahead of time though. You will need to provide the reason. Also, you might have to wait a bit, especially if your local office is small.