Sunlight and a hike may reset your internal clock better than office lighting

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age: 18-35 years * Body Mass Index: 18.5-24.9 (i.e., normal weight according to World Health Organization (WHO) criteria) * Moderate cardiorespiratory fitness levels, moderate level of endurance training according to the category "moderate physical activity" (category 2) of the International Physical Activity Questionnaire (IPAQ) short form * Informed consent as documented by signature of the participant Exclusion Criteria: * Self-reported pregnancy * Investigator's family members, employees, or other dependent persons * Chronic or debilitating medical (including psychiatric) conditions; normal state of health will be established on the basis of questionnaires and the examination by the physician in charge. Illnesses that would be a reason for exclusion are: * Sleep disorders: Narcolepsy, sleep apnea (apnea index \> 10), periodic limb movements (PLM index \> 15), insomnia (polygraphically recorded sleep efficiency \< 70% or Pittsburgh Sleep Quality Index (PSQI) index \> 5), hypersomnia * Chronobiological disorders: hypernychthemeral sleep-wake cycle, delayed or advanced sleep phase syndrome * Psychiatric disorders * Somatic diseases: cardiovascular, respiratory, gastrointestinal, haemopoietic, visual and immune system diseases, neurological disorders, infectious diseases, allergies (e.g., skin allergies, acute hay fever), thrombocytopenia or other dysfunctions of blood platelets * Drug use: volunteers must not consume any drugs (including nicotine and alcohol) for the entire duration of the study with no history of drug or alcohol dependency. This will be ensured by the use of a urine multi-drug screen at every experimental visit. * Medication that could affect outcome parameters * Shift work \< 3 months prior to study intake * Transmeridian travel (\> 2 time zones) \< 1 month prior to study intake * Extreme chronotype (Munich Chronotype Questionnaire \[MCTQ\] \<2 or \>7) * Extremely long/short sleep duration (subjective sleep duration on workdays outside 6-10h according to the MCTQ) * Abnormal colour vision, vision disorders (other than e.g., mild myopia corrected with contact lenses) * Inability to understand and/or follow procedures * Non-adherence to the circadian stabilization protocol during the five days prior to and between the experimental visits (deviation of \>30min form scheduled times more than twice or on the day of the study visit)