The long term impact of Daylight Saving Time regulations in daily life at several circles of latitude

Abstract

We analyze large scale (N~10000) time use surveys in United States, Spain, Italy, France and Great Britain to ascertain seasonal variations in the sleep/wake cycle and the labor cycle after daylight saving time -- summer time arrangements -- regulations have stood up for at least forty years. That is, not the usual search for short-term effects of the biannual transitions of DST but a search for how industrialized societies have responded to DST regulations. Results show that the labor cycle is equally distributed through seasons, an everyday experience which is a major outcome of DST. The sleep/wake cycle displays disturbance punctuated by solar events: sunrise, sunset and noon. Sleep onset in non-employees in a week-end -- the group more prone to free choices -- delays in summer opposing to the regulation. Yet, sleep offset in this group advances in summer, despite clock time already advanced in the spring transition. The best explanation for these findings is that size and directionality of DST regulations are close to an optimum. The role of latitude is discussed after sleep/wake cycle in Spain, Italy and United States exhibit fewer statistically significant excursions that the sleep/wake cycle in Great Britain and France, which could be indicating preference for time synchronization as latitude increases. The consequences of a seasonal regulation of clocks vs the choice of permanent summer time or permanent winter time is sketched from a previous report on human activity.