they try and work with you, it's hard cause alot of over the road trips
There can be a little flexibility, but many runs require you to be with a customer before a specific time. Others are more loose. If you need a dentist appointment for example, if you give the dispatcher lots of warning, you can sometimes get a shorter day or plan to start earlier.
You start, usually, at 4am. Occasionally later.
Your day ends when you finish.
Usually 8-12 hours, occasionally 14h.