Many organisms display various seasonal developmental and behavioral changes throughout the year. To know the precise time of the season, as well as upcoming seasonal changes, they measure changes in day length as a highly predictable environmental variant. Day length (=photoperiod) information is processed through the molecular network controlled by an internal timing mechanism, the circadian clock. In my lab, we are interested in elucidating the molecular mechanisms by which organisms use the circadian clock system to measure seasonal changes.