There are some excellent time-tracking apps out there, but if you prefer the comfort of good old Microsoft Excel, here's some good news. A Redditor made an Excel-based to-do list with built-in time tracking, and the template is free to download.
Write your task in the first column, your estimated time in the second column and your start time. When you're done, write down the amount of time it actually took. The rest of the sheet is automated, so it will calculate how far your estimates are from reality, and help you realise where you need to speed up or change your estimations.
Time tracking can lead to better work-life balance, and is a productivity technique suggested by several successful people. The Excel-based template is ideal to use on work computers where third-party software might not be available.