If you have forgotten to create or need to modify a reservation for a certain date and the date is already in the past, in Mews you have the possibility to still create or modify the booking.
In order to do so you need to have your editable history windows open for this date in the past.
You have 2 Editable history windows - Operational and Accounting.
The Operational one is located under Menu > Settings > Property.
The Accounting one is located under Menu > Settings > Property > Accounting configuration.
The maximum number of days for both of them is 7 days in the past and for reservations, the window starts counting as of the default check-in time you have set in your settings.