How can I display a clock in the Network Editor or in an exported *.avi video that displays the simulation second or time of day in the time format hh:mm:ss?

Show time label in the Network Editor or exported *.avi video:
Network editor > Edit basic graphic parameters > Show simulation time label

Show simulation seconds:
View > Simulation Time > Simulation Second

Show time in the time format hh:mm:ss:
View > Simulation Time > Time of Day

Set the start time of the simulation:
Simulation > Parameters > Start time