Interesting Piece of Data

I took the following notes from a source that I seem to have lost:

Professionals over-estimate what they can get done in a day, but under-estimate what they can get done in a week.

Has anyone ever heard this quote before? Does it ring true from your experience? Any evidence to back it up?

As my skills at scheduling improve over time, I find that I’m able to make better time estimates. Doing it in my calendar on Outlook/Gmail/BB is vastly superior to trying to do it ┬áin my head, which reflects some of the research findings in the post I wrote last week.