Which is the most essential tool to help you get the most done? A calendar or a to-do list?

Regarding task completion, the significant difference between a calendar and a to-do list is that the calendar accounts for time. Even minutes can be scheduled - 15-minute segments or 30 minutes. Time is precious, and a calendar will help maximize your time results.

You're forced to work within the constraints of the 24 hours that you have. Also, since there are only 24 hours a day, it reduces the paradox of choice. If you don’t get it done on the day it needs to be done, the calendar approach forces you to pick a new time.

If you can't find a place on the calendar to work on something, it will never get done by putting it on a list. The conclusion is clear: skip the to-do list, use your calendar, and break the calendar down to the most minor section of time.