Role of Photic and Non-photic Time Cues in Resetting Circadian Rhythms

Inclusion Criteria: * Aged between 18-30 years * Healthy (no medical, psychiatric or sleep disorders; * Non-smoking for at least 6 months; * Body Mass Index of \>18 or \<30 kg/m2; * Able to maintain 8-hour consistent sleep schedule during the study * Able to refrain from caffeine, alcohol, medication and supplements during the study Exclusion Criteria: * History of alcohol or substance abuse; * Positive result on drugs of abuse urine toxicology; * Current or past history of sleep disorders, including but not limited to obstructive sleep apnea, narcolepsy, insomnia, or any significant sleep complaint * Psychiatric disorder, or first degree relative with a psychiatric disorder * Recent acute or chronic medical disorder * Use of drugs or medication (birth control OK) likely to affect sleep, alertness or light sensitivity, as determined by the investigators * Visual disorder, including but not limited to color blindness, or family history of glaucoma * Pregnancy or lactation * Shift work (past 3 years) * Transmeridian travel (2 or more time zones) in the past 3 months * Any other reason as determine by the Principal Investigator