I answered a post about favorite calendar systems in the following way.
I use an Android Phone so I can google everything. I won’t use an calendar app that does not sync with google cal. and tasks. On the phone I use gtasks for tasks. Google cal. is easy because I can create as many different calendars as I like, (work, personal, kids, bills) and each displays as a different color. The biggest problem i have is no matter what calendar or task reminder I use I have ADHD and therefore the real struggle is to look at it first thing and before making commitments. I have managed to find a way to avoid every reminder but having it is much better than not.
The steno pad is the key to life. When I was fifteen I went to a boy scout camp called troop leader development. A bit like boot camp based on learning how to run a boy led troop. One aspect was that we had to always have a specific notebook with us. We called it our third arm. Who new that this concept would become so important as an adult with ADHD? My steno pad is my second brain.