Deconstructed Diary (The Week)
My solution to not finding a conventional diary useful was to embrace the fact that I was unconventional.
I like to come up with my own templates, have individual documents for different things, I like to use loose pieces of paper and write to-do lists on them. I wanted a time management system that looked like this:

Image by William Iven accessed from Pixabay 07/02/20.
So with this in mind, I have begun my creation of a 'Deconstructed Diary' that has all the essential elements of a diary spread into different documents and pages.
Week
I thought that the best place to start was with what was happening in an individual week.
I found the most essential aspect was setting aside a specific time to plan. The best day for me was Sunday. So, every Sunday I now sit down and go through what the upcoming week is going to hold. Things like how I'm going to get to where I need to go and setting time aside time for study.
I made my own sheet for this weekly planning:

Weekly planner for deconstructed diary.
I guess it would have saved a lot of time (and printing money) to just buy a planner someone else had made, but doing it myself allowed me to have a few features that were tailor made to what I like.
For example, I left a little space to name each day (things like "university day", or "work day") which is something I find useful in planning out my time. I was also able to do things like have specific slots for dinner and lunch.
It was a good start, but I still hadn't solved the problem of remembering one off events...