Simply, Go to Chandigarh Transport Website I.e chdctu.gov.in and here you find a sec 17 and sec 43 bus terminus and also a timetable , which is divided for Patiala side and shimla side and easily you view it. And otherwise if u want to book in Volvo then go on redbud.in and book the tickets. And also go for himachal pardesh site for looking about shimla bus and also find any city timetable by their official site , they mainly are a correct