Abstract: A method is for dynamically adjusting a circadian rhythm of an observer via a user device that includes control circuitry and an associated memory. The method includes determining a preconditioning schedule for at least one future event. Determining the schedule includes determining a preconditioning schedule for the at least one future events, including identifying a circadian shift needed, to the circadian rhythm of the observer, for the at least one future event, determining a timeframe for preconditioning, determining a per-day shift needed based upon the identified circadian shift needed and the determined timeframe, and determining if the needed per-day shift exceeds a threshold. Upon a determination that the per-day shift exceeds the threshold, the method includes setting the preconditioning schedule responsive to the determination to operate a light source to emit light based upon the preconditioning schedule.