I had the most productive day today, even though I was in my office for a very brief period of time. I organized my time so that I could accomplish key items on my to-do-list. I then rewarded myself with permission to take time to smell my newly seeded lawn.
I recall many a day, when I worked in corporate America, where I would sit and rearrange the papers on my desk so that I looked busy until quitting time. Of course as soon as the boss went out the door I exited.
If you are still measuring your employees in face time then you are missing the boat. Instead, try looking at results. You will be amazed how much gets done when people know they are free to leave when their work is complete.