Are you having trouble falling asleep? Are your kids hyperactive when playing with the tablet before bed time?
Are you using your smart phone or tablet in the late evening? Twilight may be a solution for you!

Recent research suggests that exposure to blue light before sleep may distort your natural (circadian) rhythm and cause inability to fall asleep.

The cause is the photoreceptor in your eyes, called Melanopsin. This receptor is sensitive to a narrow band of blue light in the 460-480nm range which may suppress Melatonin production - a hormone responsible for your healthy sleep-wake cycles.

In experimental scientific studies it has been shown an average person reading on a tablet or smart phone for a couple of hours before bed time may find their sleep delayed by about an hour.

The Twilight app makes your device screen adapt to the time of the day. It filters the blue spectrum on your phone or tablet after sunset and protects your eyes with a soft and pleasant red filter. The filter intensity is smoothly adjusted to the sun cycle based on your local sunset and sunrise times.

PRO features
- more than 2 predefined profiles
- adjustable transition time
- option to turn off Twilight service altogether during inactive times
- new features will often first appear as PRO

Thank you very much for your intention to support our development. This is a pro application for the Twilight app. Please install on top, do not uninstall Twilight first. 

Please read the basics on circadian rhythm and the role of melatonin:

http://en.wikipedia.org/wiki/Melatonin
http://en.wikipedia.org/wiki/Melanopsin
http://en.wikipedia.org/wiki/Circadian_rhythms
http://en.wikipedia.org/wiki/Circadian_rhythm_disorder

Examples of related scientific research:

        Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans
        Derk-Jan Dijk, Jeanne F. Duffy, Edward J. Silva, Theresa L. Shanahan, Diane B. Boivin, Charles A. Czeisler 2012

    Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans
    Joshua J. Gooley, Kyle Chamberlain, Kurt A. Smith, Sat Bir S. Khalsa, Shantha M. W. Rajaratnam, Eliza Van Reen, Jamie M. Zeitzer, Charles A. Czeisler, Steven W. 2011

    Effect of Light on Human Circadian Physiology
    Jeanne F. Duffy, Charles A. Czeisler 2009

    Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans
    Claude Gronfier, Kenneth P. Wright, Richard E. Kronauer, Megan E. Jewett, Charles A. Czeisler 2009

    Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans
    Kenneth P. Wright, Claude Gronfier, Jeanne F. Duffy, Charles A. Czeisler 2009

    The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work
    Nayantara Santhi, Daniel Aeschbach, Todd S. Horowitz, Charles A. Czeisler 2008

    Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina
    Farhan H. Zaidi, Joseph T. Hull, Stuart N. Peirson, Katharina Wulff, Daniel Aeschbach & Co 2007

    High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light.
    Lockley SW, Brainard GC, Czeisler CA. 2003

    Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression
    Jamie M Zeitzer, Derk-Jan Dijk, Richard E Kronauer, Emery N Brown, Charles A Czeisler 2000

    Phase-shifting human circadian rhythms: influence of sleep timing, social contact and light exposure
    J F Duffy, R E Kronauer, C A Czeisler 1996

    Exposure to bright light and darkness to treat physiologic maladaptation to night work.
    Czeisler CA..