Time Management is about more than Time
Time management is more than time management. It's managing your executive function, your day to day, your soul, and what you do. Sure, in essence it is figuring out which tasks go ahead of which tasks or what goes before what or what to tackle next but in practice it really is just....self-management.
Time management would be easy if all I had to do was throw things on a calendar. If I sum up everything I put on my calendar today, it would be ~4h, not including school and things like eating and homework and other projects. But that doesn't mean 'time management' is as simple as finding four hours of free time within my day and slotting the hours then. Instead, 'time management' is a weird combination of balancing time (how much you can physically get done), mental "action" energy1, work and play (see comic), and a bunch of other variables such as headspace (e.g. don't drive after drinking or don't schedule a lot of work grinding after taking a big test), and task strenuousness (group small tasks together; try not to get interrupted in the big tasks). With all this swirling around, I thus think that this is more than just managing time; this is managing simply your work.
And things change. I'm not at the point where I can stick to a rigorous schedule (maybe some can) but frequently these days I'm driven by some impulse. Sure, I can pencil in on the calendar "code" or "drive," but will I really go do those things? Maybe I'll be too tired from the day before, maybe I'll actually want to continue reading a book, or maybe I'll be in the midst of other things, or maybe driving doesn't feel right or something. One could say I lack discipline and rigidity, and while this is factual, perhaps the whole concept of restraining my time down was flawed from the start.
Perhaps we should rename 'time management' to just 'life management'. It's an open-ended skill that we can most likely in some respects improve on, and it most definitely deals with more than just the goddamn time. It's much easier said than done, and much easier, simpler, and is usually much often done poorly than done well. After all, it's more than just finding open time and filling it with a task.