Moorings seems to be very short sighted with their approach.

Horizon Yacht Charters handled this situation properly.
Our contract with Horizon stated final "Full" payment due 45 days before the "Charter Start Date" June 10.
Since we obviously are not going to start our charter on June 10 that is no longer our "Charter Start Date".
We moved the charter to January 2021.
Out final payment is now due 45 days before our updated Charter Start Date on Jan 4.