There are no such things as 'set times' for the passage of trains anywhere in the networks operated by freight carriers. They do have schedules they try to adhere to, that being said, on a daily basis things happen that cause trains not to operate on their schedules.
Passenger trains may operate at the scheduled times - if a paid passenger is late to the station the On Time train will be long gone. Freight transportation is different in that customer issues can cascade to effect the changes to the operation of the freight trains carrying that business.
Freight trains run when you see them, you can't set your watch by them.
Never too old to have a happy childhood!