Our staff usually doesn't work on weekends.
Job scheduling is a separate part of the production and traffic system.
It's optional, and can be started any time. It may be more practical to use it to remember upcoming deadlines and less for resource planning. Traditionally, it's been very difficult to tightly schedule creatives in the ad business. Unlike building airplanes, creatives don't fit well into rigid work schedules. In fact, since job scheduling is so time-consuming it's a good idea to use it for only large, complex jobs with long time lines.