"I live and die by my calendar," Herjavec tells CNBC Make It.
And he always tries to plan 12 months ahead.
"[It] allows me to manage my time and prioritize," he explains. "It doesn't mean that everything on the calendar needs to be locked in, but it gives me an idea of where I'm going to be and when so I can maximize my time."
For example, to stay on top of his kids' schedules when they were young, Herjavec would meet with the school's counselors and plan for their activities a year in advance, he tells Entrepreneur.
"Because of that, I never missed a swim meet. I never missed a school play. I never missed anything," he says.
Herjavec's calendar also helps with his day-to-day efficiency. "The details, the briefs are always all there," he says. "It helps me be prepared, and I always have a reference."
He suggests that everyone use their calendars more rigorously.
"Set aside time to do a full calendar review six months or a year out to make sure you are on track with your yearly goals as well," he tells Fortune.