Hello Abdelrahman
You will find all information about the Saver Day Passes as well as the synoptic Map > Downloads under this link.
It is valid on the GoldenPass line. Seat reservations can be done here.
Save Day Passes are valid on the selected day (midnight) up until 5 a.m. the following day (29hours)
Hope I could help you with this information and wish you an unforgettable staying in Switzerland.
Regards RahelW