The format of the clock can be changed using the clock button Data & Rules tab or by double-clicking the clock window.
The clock can be digital or analog and can show information about the day and week or percentage of run complete. It can be docked at any location on the toolbars, or at the margins of the Simulation Window.
The clock dialog can also be used to set the time that work starts each day (and how long the day is). More detail for such information can be placed in your simulation using Shifts.
The simulation time units set in the clock are global. Any times entered elsewhere in the simulation are in the time units entered in the clock dialog.
If speed of your simulation is a concern the clock can be updated in a more computer-efficient (but less visually appealing) manner - see the High Speed Clock.
The clock is so important it's one of the few windows in Simul8 that can never be closed.
For more guidance on setting up the Clock, see the Clock Setup Tutorial.