@Willy-and-Laci0 While it is still possible to edit your calendar for all of 2021, I think what you're experiencing is a 12-month maximum advance for bookings (in the past, guests could only book up to 12 months ahead, but I can't find a policy notice confirming that this is still the case). If the planned checkout date is June 20 of next year, the date you'd be able to complete the change request is June 21 of this year.
In the meantime, if you're anxious to get the calendar dates open, you could coordinate with the guests and agree on a place-holder date to move the booking to, with a view toward moving it again when the real dates are within the 12-month window. It does complicate things a bit with the back-and-forth of change requests and confirmations, and perhaps increases the risk that something will go wrong in the system. Personally, I'd just wait until later this month to do the change, since there's still all of July to fill out the August calendar.
