Circadian Clock & Light Resetting Awareness

An interactive application designed to demonstrate how environmental light acts as a zeitgeber (time giver) to physically recalibrate the human master biological clock.

By inputting a user's natural wake window, this app uses established chronobiology formulas to map out an individual’s Phase Response Curve (PRC), identifying exact personal timing windows for shifting or stabilizing sleep patterns.

🛠️ How to Use

1. Input Data: Enter your Natural Wake Time.
   • Note: This must be the time you wake up naturally when you are fully rested (e.g., on a weekend or holiday without an alarm clock).
2. Calculate: Click "Calculate My Custom Curve" to dynamically populate your personal timeline, interactive graph, and lifestyle guide.

🧠 Under the Hood: Biological Assumptions

This application leverages standardized parameters derived from clinical sleep science and chronobiology research:

1. The Anchor Point (CBTmin)

The master clock inside the brain's Suprachiasmatic Nucleus (SCN) tracks internal time using metabolic markers. The definitive anchor for this timeline is the Core Body Temperature minimum (CBTmin). In clinical environments, CBTmin consistently occurs approximately 2.5 hours prior to a person's unforced, natural wake time.

2. The Phase Response Curve (PRC) Mapping

Once CBTmin is established, the application splits the 24-hour cycle into three distinct functional zones based on how light exposure shifts the molecular cycle of core clock genes (Per and Cry):

• The Phase Delay Zone (6 Hours Prior to CBTmin): Light exposure here forces the master clock to register that "the day is longer than expected." This pushes your biological bedtime backward, meaning you will naturally feel tired later that night and want to sleep in later the next morning.
• The Phase Advance Zone (6 Hours Post CBTmin): Light exposure here tricks the SCN into identifying an early dawn. This pulls your biological clock forward, meaning you will naturally feel sleepy earlier that night and wake up easily earlier the following morning.
• The Circadian Dead Zone (Remaining 12 Hours): Daytime light exposure that yields near-zero directional shift. Light received here instead scales the amplitude of your circadian cycle, driving robust daytime alertness and deeper sleep onset at night.