BeginOfCurrentDay is a specific point in time, so unless you have a record whose BookingDate is exactly equal to that point in time, you won’t have any records returned. Try [BookingDate >= ‘[%BeginOfCurrentDay%]’] which should show all records whose booking date is after the beginning of the current day.
[BookingDate >= '[%BeginOfCurrentDay%] + [%DayLength%]'] does also not work. Still all future dates are in the grid.
[BookingDate >= '[%BeginOfCurrentDay%]' and BookingDate <= '[%EndOfCurrentDay%]'] shows me all bookings for tomorrow, the 11. June?