The arrival date shows the year 1900 or 0001, there is no additional information in the reservation, or you do not know what the original reservation is.
If you check the reservation in the Channel Manager, you'll see the following message in the comment: ''Note: the original booking could not be found'' or "Note: the original booking data is not available".
Most of the time, this kind of messages mean that the original reservation is not in the Channel Manager, so the cancellation or modification cannot be linked to any reservation in the system. In these cases, you have to keep in mind that the availability is not updated and you will have to do this manually.
Example 1 (reservation notification received by e-mail)
Example 2 (reservation overview in the Channel Manager)