Ask HN: What do you use for personal planning?

Is there an all-in-one program for keeping a tasklist, calendar, and monthly budget, that allows each of these to access data from the others?

Do you have a hundred-page spreadsheet which you control like a switchboard operator that replicates this functionality?

Do you have a big sheet of paper that you write all over and replace at the end of the month?

So often I've thought of a project I'd like to do or plans I should make with somebody and I've ended up forgetting. I feel like when I do note things down, they end up scattered across my notebook, laptop, desktop, phone, and brain. So I'm wondering if some of you have found success with some overarching system that helps you keep track of anything. The closest thing I can think of is Obsidian, which I've found to be incredible for storing written notes, but I feel like it's limited in its capability to plan things into the future. I'd love to be proven wrong, though!