Can shifting time by one hour each day reset your internal clock?

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

Inclusion Criteria * Healthy adults aged 23-45 years * Part of a heterosexual, cohabiting couple willing to participate together in a five-day in-laboratory study * Both partners meet all inclusion criteria * Completion of at least upper-secondary education * Maintain a regular sleep-wake schedule * Habitual sleep timing within a normative range (non-extreme chronotype), assessed using the Morningness-Eveningness Questionnaire (MEQ) or the Munich Chronotype Questionnaire (MCTQ) * Both partners fall within the acceptable chronotype range to ensure aligned sleep-wake patterns * Low seasonality scores on the Seasonal Pattern Assessment Questionnaire (SPAQ) * Free from underlying sleep or mood disorders Exclusion Criteria * Engages in night-shift work or maintains an irregular work or sleep schedule * International travel involving a time-zone change of more than two hours within the past two months, or anticipated travel before study completion * Diagnosed neurological, psychiatric, or sleep disorder (e.g., insomnia, sleep apnea, bipolar disorder) * High risk of sleep apnea, defined as a Berlin Questionnaire score \>2 (Lauritzen et al., 2018) * Use of medications known to affect sleep, alertness, melatonin secretion, or circadian timing * Unable or unwilling to comply with behavioral restrictions, including refraining from electronic devices displaying time cues unless clocks are removed and devices are disconnected from Wi-Fi * Unable or unwilling to comply with consumption restrictions, including abstaining from caffeine, alcohol, and melatonin-rich foods during the study * Extreme chronotype, defined as a habitual midsleep time outside 03:00-05:00 on the MCTQ or classification as an extreme morning or extreme evening type on the MEQ * Daily caffeine consumption exceeding 400 mg (approximately 4-5 cups of coffee) * Current smoker or smoking within the past six months