If the answer is NEVER then you’re doing it wrong.

Seriously. Check this out:

Time Management: How an MIT postdoc writes 3 books, a PhD defence, and 6+ peer-reviews papers. And finishes by 5:30pm.

You see you can’t really manage time. You can’t save it, spend it or do anything with it or to it. You have the same 24 hours a day that Bill Gates, and your cat have.

What you can manage is yourself and what you do or don’t do WITHIN the time you have. It’s a great article. Click and read it if you haven’t already.