25199

We found out that if you divide 1000 by 7 you would get 142.85. So we rounded it to 142. We then multiplied 142 by 7 to get 994. This is just 6 days form the 1000th day from Monday. So we added 6 days from the monday which was scheduled in 994 days. this then gave us the day of Sunday. so we came to the solution that the 1000th day of the said Monday will be on a Sunday.