I started using a planner in grad school. I think it was a Daytimer sort of thing, with lots of pockets, and business card holder, and sections. I kept using that until I started teaching. I talked about my bullet journal journey in my comment to Day 1, I think.

As many people have said above, digital calendars are convenient, but nothing beats the tactility of writing things down. And it helps my memory to handwrite also.