Longitudinal Location Influences Preference for Daylight Saving Time

Abstract

The chronobiology community advocates ending the biannual practice in many countries of adjusting their clocks to observe Daylight Saving Time (DST). Many governments are actively considering abandoning this practice. While sleep and circadian experts advocate the adoption of year-round standard time, most jurisdictions are instead considering permanent DST. In guiding advocacy, it is useful to understand the factors that lead governments and citizens to prefer the various options. In October 2021, the Canadian province of Alberta conducted a province-wide referendum on adopting year-round DST, in which more than 1 million valid votes were cast. As this referendum was tied to province-wide municipal elections, the results of the referendum were reported at the community level, allowing a geospatial analysis of preference for permanent DST. While the referendum proposal was narrowly defeated (49.8% in favor), a community-level analysis demonstrated a significant East-West gradient, with eastern communities more strongly in favor and western communities more strongly opposed to the year-round DST. Community size and latitudinal position also contributed to preference, with smaller and more northern communities showing more preference for year-round DST. These findings help identify how geospatial location can influence how citizens feel about the various time options and can further help guide public advocacy efforts by the sleep and circadian communities.

Keywords: daylight saving time; latitude; longitude; standard time.

Figure 1.

(a) Geographic location of the province of Alberta relative to the ideal location of the time zone it follows during StdTime (UTC-7, 105°W). (b) Offset of the 30 most populous Canadian cities from the time zone they follow when on StdTime. Longitude location was subtracted from the meridian that defines the time zone followed (i.e. 52.5°W, 60°W, 75°W, 90°W, 105°W, 120°W for UTC-3.5, UTC-4, UTC-5, UTC-6, UTC-7, and UTC-8, respectively). Green shading represents offsets where solar noon occurs ±30 min of 1200 h. Communities outside this range are named, and Alberta communities are shaded. Black-filled circles represent Alberta communities when following StdTime, while red-filled circles represent these same communities if following pDST. (c) The geographic location of the communities and their color-coded votes in the 2021 DST referendum. Green represents communities where >50% voted in favor of pDST, while red represents communities where <50% of voters were in favor of pDST. Abbreviations: UTC = Universal Coordinated Time; pDST = permanent Daylight Saving Time; DST = Daylight Saving Time.

Figure 2.

(a) Graph presenting the Multiple Linear Regression analysis showing the relationship between latitudinal and longitudinal position and the % vote in favor of pDST. The mesh plane represented the output of the best-fit multiple linear regression analysis. (b) Simple Pearson’s correlations depicting how % vote in favor of pDST correlates with Longitudinal Position, Latitudinal Position, and Number of Votes Cast (as a metric for the population of district). Abbreviation: pDST = permanent Daylight Saving Time.