Biological Clock Calculator

Circadian rhythm driven by melatonin (hormone that peaks 2–3 hours before sleep). Light suppresses melatonin; darkness triggers it. Jet lag = circadian misalignment.

Light exposure critical: bright light 6 AM (phase advance sleep), dim by 9 PM (allow melatonin rise). Takes 3–7 days per hour of shift. Avoid screens 1 hour before bed.

Mostly genetic (15–20% of population naturally later). Adolescents shift 1–2 hours later (circadian phase delay). Adults past 30 shift earlier. Shift work causes chronic circadian misalignment.