I shamefully admit that I lost track of the level of IT support for this feature (same day change on short haul for EBDs/PLUS). I would like to try using it on Monday, where I am booked for an evening departure, but would prefer a late morning departure. Will the option open in the app or on the website at some known point in time? Only on Monday? Should I check in first for my evening departure, or better not to, because I will lose the option?

I am not too eager to go to the airport Monday morning, just to discover that I failed, and need to wait until my evening departure