Sunlight to Reset your Internal Clock

If you ever find yourself having trouble sleeping at night and feeling tired during the day, don’t forget that your internal clock is set based on sunlight.  Getting even just 15 minutes of direct sunlight every day can do a lot to help reset your internal clock if you are coming from another timezone or have just messed your schedule up by working a bunch of late nights.


Sunlight can also help you when you are feeling tired.  It is amazing how much you can improve a sluggish afternoon just by opening the blinds and getting some direct sunlight into the room or taking a 10 minute walk outside in the light.

I’m not sure if sunlight works best because of the spectrum or if it is just the intensity.  You can get some benefit from artificial lighting, but I’ve never been able to duplicate the full effect of sunlight.  We usually underestimate just how powerful sunlight is and most well-lit offices are still extremely dark compared with being outside on a bright day.

Originally published April 7, 2007.


  1. says

    I have experienced this regularly. The problem I face is during dark gloomy days I get so tired I can barely function. I live in Florida and we had been having Spring until the last few days and my energy has plummeted as the clouds moved in. I wish there was a way to replicate the sun for 15 minutes a day.

  2. says

    @Brian – You might try getting some of those light bulbs for plants and put them in your office. Five 100 watt bulbs should brighten up a room pretty well. I don’t know if it will work, but I find that when I’m getting tired, I can often get some more energy just by turning on a brighter light. In fact I have a 120 watt flood lamp attached to a shelf near my desk that I use for this.

    Good luck and let me know if you find anything that works well for you.

  3. Evol. says

    >I’m not sure if sunlight works best because of the spectrum or if it is just the intensity. You can get some benefit from artificial lighting,…

    It’s mostly the intensity. Volkswagen in Wolfsburg, Germany have much improved the quality of their night shift work with drastically brighter lighting.

    Also the color plays a role. We are evolutionary heirs of animals going to sleep when the sky got reddish and being wide awake when there was much blue. If you do late computer work and want to fall asleep soon after, set the screen to a warm color temperature (reddish-brown). For staying awake set it to cool bright blueish.

  4. says

    Hey you can put the plugin to share some articles like twitter or facebook buttons?? haha i can make it manualy but can be easer the first way, thanks

  5. says

    Great article! I agree and may also add, that it is the hours before midnight that is also important in achieving a good nights rest. I used to balk at this as a younger child, but now I firmly agree with my parents wise words of advice.

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