I recommend not only track your time, but also write down what you do, and have project-names. Using this I can give very accurate estimates by going back and s

I recommend not only track your time, but also write down what you do, and have project-names. Using this I can give very accurate estimates by going back and see how long time things took. And it makes it easier to plan things. Also if you are in an early startup it's good to have this so your co-founders know how much you work and on what. And if you are employed you can use it to tell your boss exactly what you did (and why it took so long). There's a saying though, that you'll spend 50% of your time documenting what you do.