Personal Planner is a free, open-source daily planner for Windows, macOS, Linux and Android. Plan your day in time blocks, time your tasks, and compare what you planned with what actually happened.
I built it because I kept setting aside 30 minutes for a task, spending an hour on it, then making the same estimate the next day. Daily and weekly reviews keep your tasks, actual time and notes together, so you have something useful to look back on.