It’s been a pain.

I booked some time in March 2024.
The first segment had to be correct - so our ticket started 19 January 2025.
And each subsequent segment had a dummy date over the next several weeks with the last segment flown slotted on the last eligible day one year after the booking date.

Down side of this is seasonal flights are not necessarily available so can’t be booked. I wanted DFW-YUL but apparently no one wants to fly to Montreal in February, brrh.