In the video, the month of the first object (day1) was March. That's because the video was recorded on that day. When you ask for the month of your day1 object, it will say October. When you ask for the current day of the month, it will say whatever the current day is. 

Because your day1 object is different from the day1 object in the video, when you add 100 days to it, the result will be different from the result in the video.

Be careful when you create day2. You are asked to specify November as the month. You must use the integer 11 rather than "Nov" or "November". If you try to use the name of the month, an error message will appear.