The present invention relates to a computer implemented method for scheduling light therapy to prevent symptoms of jetlag when travelling across multiple time zones. The invention further relates to a system for preventing symptoms of jetlag of a user travelling across multiple time zones. One embodiment discloses a computer implemented method for calculating a schedule of bright light treatments for preventing symptoms of jetlag when crossing a number of time zones during travelling, the method comprising calculating a schedule of doses of bright light beginning at the day of arrival, each dose separated by an interval of between 2 and 4 hours, such as 3 hours, wherein when travelling west the time of the first dose at the day of arrival is scheduled during the forenoon between 11 and 13 oclock, such as 12 oclock, and when travelling east the time of the first dose at the day of arrival is scheduled at around x+7 oclock if crossing less than six time zones, and at around x oclock if crossing at least six time zones, where x is the number of time zones crossed.
