Are you struggling to fall asleep at night? Do your children seem overly energetic after using their tablets before bedtime? If you're using your smartphone or tablet in the evening or are sensitive to light during migraines, Twilight might be the solution you need!

Recent research indicates that exposure to blue light before sleep can disrupt your natural circadian rhythm, making it harder to fall asleep. This is due to a photoreceptor in your eyes known as Melanopsin, which is sensitive to blue light in the 460-480nm range. This light can suppress Melatonin production, a crucial hormone for maintaining healthy sleep-wake cycles. Studies have shown that reading on a tablet or smartphone for a few hours before bed can delay sleep by about an hour.

Twilight is designed to help by adapting your device's screen to the time of day. It filters out blue light after sunset, protecting your eyes with a soft, pleasant red filter. The intensity of this filter adjusts smoothly according to your local sunset and sunrise times.

You can also extend Twilight's benefits to your Wear OS device for a consistent experience.

Documentation

For more detailed information, visit: http://twilight.urbandroid.org/doc/

Get More from Twilight

1. Bed Reading: Twilight provides a more comfortable reading experience at night. It can dim the screen beyond the capabilities of standard backlight controls.

2. AMOLED Screens: Extensive testing on AMOLED screens over five years shows no signs of depletion or over-burning. Proper configuration of Twilight results in less light emission and a more even light distribution, which may extend your screen's lifespan.

Basics on Circadian Rhythm and Melatonin

For a deeper understanding, explore these resources:

• 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

Permissions

• Location: To determine your local sunset and sunrise times.
• Running Apps: To disable Twilight in selected apps.
• Write Settings: To adjust the backlight.
• Network: To connect with smart light systems like Philips HUE to reduce blue light in your home environment.

Accessibility Service

To filter notifications and your lock screen, Twilight may request the use of the Accessibility Service. This service is used solely to enhance screen filtering and does not collect any personal data. Learn more at: https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/

Wear OS

Twilight syncs with your Wear OS device, allowing control over filtering through a "Wear OS Tile".

Automation (Tasker or other)

For advanced users, explore automation options at: https://sites.google.com/site/twilight4android/automation

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, et al. (2012)
• Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans - Joshua J. Gooley, et al. (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, et al. (2009)
• Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans - Kenneth P. Wright, et al. (2009)
• The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work - Nayantara Santhi, et al. (2008)
• Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina - Farhan H. Zaidi, et al. (2007)