The key was to realize that there is a difference between a calendar, a todo list, and an agenda.
A todo list is a list of things that need to be done but usually don’t have a specific time when they need to be done at. They can have priorities or deadlines or fuzzy target dates like “next week.”
A calendar is for storing future concretely scheduled events.
An agenda is a list of things that will happen soon.
Each day I pull things from my calendar, todo list, and prior agenda and create my daily agenda. I also keep notes, doodles, clippings, and references in my agenda.
I use Google calendar as my calendar. It meets my expectations.
For my todo list I use Notion. I break it down into “next, soon, and later”. I add ad-hoc sections like “after the vacation” when needed. Some todo items are scheduled for a specific day or “not sooner than.” I add these to my calendar with an email reminder so they don’t take up any mind space until needed.
Finally, the daily agenda. I use Notion but could probably use a physical notepad. I like being able to archive them as sometimes I need to check when I did something or pull some details from notes. With a digital agenda I can file it into an archive easily.
This is not perfect but it helped me reconcile the rigidity of calendar tools with the need to do keep things freeform in the short term.