Jose Maria Martin-Olalla

arXiv2026

Methodological guidelines for circadian modeling of Daylight Saving Time: application to the United States

Modeling the circadian impact of seasonal clock changing requires precise synchronization between solar and social time. This report critiques a recent study that associated disease prevalence in the United States with seasonal clock exposure. We identify a fundamental computational error in which a sign reversal of the longitudinal offset effectively inverted the US East-West axis, cross-correlating local health data with the circadian burden of hypothetical locations on the opposite side of a time zone. We outline the methodology for a correct modelization of the circadian process in the context of US geography.

physics.soc-ph↗

arXiv2019

Comment to Impact of Daylight Saving Time on circadian timing system: An expert statement

1000 words comment on a paper published in the European Journal of Internal Medicine by a panel of experts. My point is authors address the magnitude of the change (one hour) but fail to consider in any way its seasonal features. DST is not a random change of an hour but an specific change on specific dates and in a specific direction ---spring forward, fall back---. DST is the way many contemporary societies handles the seasonality. The way many contemporary societies turn a nonseasonal clock (the mechanical clock) into a seasonal clock.

physics.pop-ph↗

arXiv2017

Latitudinal trends in human primary activities: characterizing the winter day as a synchronizer

This work analyzes time use surveys from 19 countries (17 European and 2 American) in the middle latitude range from 38° to 61° latitude accounting for 45% of world population in that range. Time marks for primary activities (sleeping, working and eating) are systematically contrasted against light/dark conditions related to latitude. The analysis reveals that winter sunrise is a synchronizer for labor start time below 54° where they occur within the winter civil twilight region. Winter sunset is a source of synchronization for labor end times. Winter terminator also punctuate meal times in Europe with dinner times occurring 3h after winter sunset time within a strip of 1h, which is 40% narrower than variability of dinner local times. The sleep-wake cycle of laborers in a weekday is shown to be related to winter sunrise whereas standard population's cycle appears to be irrespective of latitude. The significance of the winter terminator depends on two competing factors average daily labor time (some 7h30m) and winter daytime ---the shortest photoperiod---. Winter terminator gains significance when shortest photoperiod roughly matches to daily labor time plus a reasonable lunch break. That is within a latitude range from 38° to 54°. The significance of winter terminator as a source of synchronization is also related to contemporary year round time schedules: the shortest photoperiod represents the worst case scenario the society faces. Average daily sleep times show little trend with the shortest photoperiod slope 5min/h for a Pearson coefficient $r^2=0.242$. Average labor time may have a weak coupling with the shortest photoperiod: slope 29min/h for $r^2=0.338$.

physics.soc-ph↗