The calendar must be a sacred ground. Do not put too much stuff there, or you will lose trust in the process.

What needs to go in the calendar? We definitely need to put scheduled meetings. This is the hour scale, when we already know a date and a time (and possibly a duration) at which a given event will take place.

Other things that need to go in the calendar are tasks that need to be completed on a certain day. It does not matter when during the day, but they need to be done. These tasks should have no time assigned, but definitely a date. This is the day scale At the beginning of the day, they can be hour-scheduled at a convenient time. But why stop at the day frame? Some things can be only be hour-scheduled when other tasks have populated the agenda. But perhaps we can even introduce a week scheduling in which things that need to be done on a certain week are assigned to the correct day. Ideally there is a balance between the number of tasks that need to be assigned and the required fine-graininess.