Le décalage horaire refers to the time difference between places. Usually the time difference between Philadelphia and France is six hours. However, for the past week, le décalage horaire has only been five hours. That’s because the French ended Daylight Saving Time (l’heure d’été) on Oct. 31, while the US changes its clocks this Sunday. Likewise between March 14th (when the US moved clocks forward) and March 28th (when France did), there was also a difference of 5 hours between Philly and France.
Oh, and if you’re in the US, don’t forget to change your clocks.