To say this differently, currently this Tuesday and every two weeks, I'm occupied from 12:00 Eastern time to 13:30 (which might also run slightly longer sometime).
In between there there's a meeting that might not always run as long, so 30mins earlier might be "ok", but otherwise I could miss the first 15 mins of the office hours.
Moreover the 13:00, to 13:30 meeting could change cadence, but I don't know on which week it will land.
All the Tuesdays of the other weeks I'm empty (except now for this weekly meeting, which I'm not sure which week will end up when and if it will slow down).