If you're a photographer, you're not going to plan to capture the perfect sunset next Friday at 6:03PM. You grab your camera when the clouds are breaking and the light is golden and the moment is calling.
If you're a bird watcher, you're not going to tell the birds to show up between 3 and 4 PM tomorrow. You venture out when migration patterns align and weather conditions are right and patience is on your side.
Some things you can schedule. Others, you need to be ready for them and react.
You can't pencil in when you do accessibility. You do it when you need to. Better yet, you do it as part of your daily routine and you know it'll get done.
It then becomes business as usual.