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

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 regulations have stood up for at least forty years. That is, not the usual search for the impact of the biannual transitions, but a search for how industrialized societies have answered to DST regulations at different circles of latitude. Results show that the labor cycle is equally distributed through seasons if measured in local time. It is an everyday experience which is a major outcome of DST. The sleep/wake cycle displays disturbances punctuated by solar events: sunrise, sunset and noon. In week-ends, under free preferences, sleep onset delays in summer, opposing to the regulation and following the delay in sunset time, while sleep offset advances, despite clock time already advanced in the spring transition. This advance still follows the advance in sunrise times. The best explanation for these findings is that human cycles are not misaligned by the size and direction of DST regulations, which explains the success of that practice. The sleep/wake cycle in Great Britain and France exhibit fewer statistically significant excursions than the sleep/wake cycle in Spain, Italy and United States, despite light and dark seasonal deviations are larger. That could be indicating that the preference for a seasonal regulation of time decreases with increasing latitude above 47°. The preferences for a seasonal regulation of clocks and for the choice of permanent summer time or permanent winter time are sketched from a previous report on human activity.