Timing of assignment deadlines and examinations relates to sleep, well-being, and academic performance.

Time-of-day can affect optimal performance in educational and professional settings.Although institutional schedules such as early morning classes are known to negatively affect sleep and academic outcomes, the impact of assignment deadlines and examination timings is less clear.Here, we examined how the timing of 16,677 assignment deadlines and 1,371 examinations associated with sleep, wellbeing, and academic performance in a cohort of 636 first-year undergraduate students over their first semester at university.Sleep was objectively tracked using a wearable device, whereas well-being was assessed through daily smartphone-delivered ecological momentary assessments.We found that nearly half (44%) of total assignments were submitted within 24 hr of its deadline.Those due earlier in the day were associated with 11-49 min shorter sleep the night before the deadline compared with a typical night.Sleep satisfaction was also poorer with earlier deadlines, whereas stress and sadness levels were highest on days with early morning deadlines.Furthermore, morning examinations were associated with 61-82 min shorter sleep than both afternoon and evening examinations.However, both morning and evening examinations were associated with 5-6 percentage points poorer course grades on average compared with examinations commencing in the afternoon.Regardless of examination time-of-day, sleep the night before an examination was associated with course performance.Notably, each hour less sleep than habitual the night before an examination was associated with a 1.2-to 3-percentage point decrease in marks achieved.These findings suggest timing of assignment deadlines and examinations as a key modulator of student sleep, well-being, and academic success. Educational Impact and Implications StatementLast-minute submissions of student assignments due earlier in the day were linked to shorter and poorer quality sleep, and reduced well-being.Both morning and evening examinations were associated with poorer academic performance compared with afternoon examinations, but scores were moderated by sleep duration the night before.