Timing a day trip
A realistic plan: leave at 7–8 a.m., about three hours on the road, two to three hours in the canyon including the descent into the valley and the climb back, returning to the city by 6–7 p.m. That is 10–12 hours, so the trip is priced as a day booking.
In summer the canyon is hot and shadeless at midday — an early start is far more comfortable. In spring and autumn the timing is looser, but it gets dark sooner.