The hidden toll of longer evenings: BC’s experiment with transitioning to permanent daylight saving time

British Columbia transitioned to permanent daylight saving time (DST) as of Sunday, 8 March 2026. This move has received some criticism, with one researcher calling it “scientifically not a good idea.”[1] Similarly, OHS Canada indicated that “in its switch to permanent daylight time, BC got it wrong.”[2]

The switch in BC was partly informed by a 2019 provincial survey in which over 90% of approximately 223 000 respondents supported adopting permanent DST.[3] However, permanent standard time (ST) was not offered as an option—respondents could choose between permanent DST or continuing with biannual clock changes. In its rationale, the Government of BC mentioned anticipated benefits including improved overall health; fewer disruptions to sleep patterns, daily routines, and schedules; and longer daylight in the evenings to support leisure and economic activity.[3] In a 2019 letter to then premier John Horgan, the BC Chamber of Commerce suggested that ending biannual changes would also be associated with reductions in workplace and traffic accidents.[4]

The Government of BC website links to a study from the Stanford University School of Medicine supporting its rationale to move to permanent DST.[3] The authors of the study suggest that biannual shifting results in the greatest burden on circadian rhythms, when compared with either permanent ST or permanent DST.[5] As indicated by Dr Schwandt in his May BCMJ editorial,[6] other studies have also shown an association between the transition to DST and a modest increase in acute myocardial infarction,[7] stroke,[8] poor sleep and mood disturbances,[9] and traffic accidents.[10]

The choice of which permanent time to adopt, DST or ST, is not to be taken lightly. For instance, the Stanford University study revealed that, when comparing the two options, permanent ST was more likely to result in a decrease in the prevalence of obesity (−0.78% [−0.06% to −1.49%]) and stroke (−0.09% [−0.04% to −0.14%]) compared with DST (−0.51% [−0.09% to −0.93%] and −0.07% [−0.04% to −0.09%], respectively).[5] While direct evidence on the long-term effects of permanent DST remains limited, there is growing recognition that misalignment between social and biological clocks, so-called social jet lag, can persist for several months beyond the initial transition period to DST.[11] Permanent DST effectively delays morning light exposure, particularly during winter months, when the sun may rise as late as 9 a.m. in cities such as Vancouver and Victoria. Alternatively, permanent ST allows for better alignment of our internal circadian clock with the social clock, reducing the risk of social jet lag.[12] Social jet lag has been associated with increased risk of elevated BMI, metabolic syndrome,[13,14] and mood deficits.[15] Professors in the UBC School of Nursing have published on this topic, indicating that “BC’s switch to permanent DST adds to the ‘perfect storm’ for poorer adolescent sleep and mental health.”[16] Multiple professional bodies, including the Canadian Sleep Society, American Academy of Sleep Medicine, European Biological Rhythms Society, European Sleep Research Society, and Society for Research on Biological Rhythms, support permanent ST as the best option in terms of public health and safety.[17-19]

However, potential benefits of permanent DST should not be dismissed. Extended evening daylight may promote physical activity, social engagement, and economic activity, particularly in areas such as tourism and retail. However, anticipated energy savings remain uncertain and may be offset by increased consumption related to extended evening activities.

For physicians and surgeons, many of whom start work early in the day, permanent DST can contribute to misalignment with the circadian clock. Delayed morning light exposure, combined with early start times and demanding schedules, may result in further sleep deprivation, fatigue, and impaired cognitive performance. At the same time, longer, brighter evenings may encourage later bedtimes, further contributing to sleep deficits.

On a personal note, I find permanent DST appealing in some ways. It allows the opportunity for many people, including physicians, to spend evening time outdoors in daylight and engage in social and recreational activities after work, which, in my opinion, contributes significantly to quality of life. As stated by Dr Schwandt in his editorial, these benefits, while difficult to quantify, are not trivial. Indeed, individual preferences, lifestyles, and chronotypes may influence how such a policy is experienced by everyone.

Ultimately, the decision to eliminate biannual clock changes appears reasonably supported from a public health and safety perspective. Whether BC selected the optimal approach, however, is to be determined as we embark on this natural experiment.
—Sepehr Khorasani, MD, MSc, FRCSC

References

1.    Carman T. ‘Scientifically not a good idea,’ says researcher whose work informed B.C.’s daylight-time decision. CBC News. 5 March 2026. Accessed 13 April 2026. www.cbc.ca/news/canada/bc-daylight-saving-health-concerns-9.7114947.

2.    Harnett M. In its switch to permanent daylight time, B.C. got it wrong. OHS Canada. 6 March 2026. Accessed 13 April 2026. www.ohscanada.com/opinions/in-its-switch-to-permanent-daylight-time-b-c-got-it-wrong/.

3.    Government of British Columbia. Permanent daylight saving time. Updated 23 March 2026. Accessed 13 April 2026. www2.gov.bc.ca/gov/content/governments/celebrating-british-columbia/daylight-saving-time.

4.    Litwin V. Submission on time observance and maintaining daylight saving time (DST) year-round. Letter to the Honourable John Horgan from the BC Chamber of Commerce. 19 July 2019. Accessed 7 April 2026. https://engage.gov.bc.ca/app/uploads/sites/121/2020/03/BC-Chamber-of-Commerce.pdf.

5.    Weed L, Zeitzer JM. Circadian-informed modeling predicts regional variation in obesity and stroke outcomes under different permanent US time policies. Proc Natl Acad Sci USA 2025;122:e2508293122. https://doi.org/10.1073/pnas.2508293122.

6.    Schwandt M. Shining light on permanent daylight saving time and health. BCMJ 2026;69:122,124.

7.    Manfredini R, Fabbian F, De Giorgi A, et al. Daylight saving time and myocardial infarction: Should we be worried? A review of the evidence. Eur Rev Med Pharmacol Sci 2018;22:750-755. https://doi.org/10.26355/eurrev_201802_14306.

8.    Sipilä JOT, Ruuskanen JO, Rautava P, Kytö V. Changes in ischemic stroke occurrence following daylight saving time transitions. Sleep Med 2016;27–28:20-24. https://doi.org/10.1016/j.sleep.2016.10.009.

9.    Berk M, Dodd S, Hallam K, et al. Small shifts in diurnal rhythms are associated with an increase in suicide: The effect of daylight saving. Sleep Biol Rhythms 2008;6:22-25. https://doi.org/10.1111/j.1479-8425.2007.00331.x.

10.    Robb D, Barnes T. Accident rates and the impact of daylight saving time transitions. Accid Anal Prev 2018;111:193-201. https://doi.org/10.1016/j.aap.2017.11.029.

11.    Hadlow NC, Brown S, Wardrop R, Henley D. The effects of season, daylight saving and time of sunrise on serum cortisol in a large population. Chronobiol Int 2014;31:243-251. https://doi.org/10.3109/07420528.2013.844162.

12.    Antle MC. The controversy over daylight saving time: Evidence for and against. Curr Opin Pulm Med 2023;29:574-579. https://doi.org/10.1097/MCP.0000000000001003.

13.    Roenneberg T, Allebrandt KV, Merrow M, Vetter C. Social jetlag and obesity. Curr Biol 2012;22:939-943. https://doi.org/10.1016/j.cub.2012.03.038.

14.    Koopman ADM, Rauh SP, van ’t Riet E, et al. The association between social jetlag, the metabolic syndrome, and type 2 diabetes mellitus in the general population: The New Hoorn Study. J Biol Rhythms 2017;32:359-368. https://doi.org/10.1177/0748730417713572.

15.    Short MA, Booth SA, Omar O, et al. The relationship between sleep duration and mood in adolescents: A systematic review and meta-analysis. Sleep Med Rev 2020;52:101311. https://doi.org/10.1016/j.smrv.2020.101311.

16.    Keys E, Hall W. BC’s switch to permanent DST adds to the ‘perfect storm’ for poorer adolescent sleep and mental health. The Conversation. Updated 12 March 2026. Accessed 13 April 2026. https://theconversation.com/b-c-s-switch-to-permanent-dst-adds-to-the-perfect-storm-for-poorer-adolescent-sleep-and-mental-health-277587.

17.    Rishi MA, Ahmed O, Barrantes Perez JH, et al. Daylight saving time: An American Academy of Sleep Medicine position statement. 2020;16:1781-1784. https://doi.org/10.5664/jcsm.8780.

18.    European Biological Rhythms Society, European Sleep Research Society, Society for Research on Biological Rhythms. To the EU Commission on DST. Letter to the EU Commission. Accessed 13 April 2026. https://esrs.eu/wp-content/uploads/2019/03/ To_the_EU_Commission_on_DST.pdf.

19.    Canadian Sleep Society. Position statement of the Canadian Sleep Society on the practice of daylight saving time (DST). Accessed 13 April 2026. https://css-scs.ca/society-news/position-statement-of-the-canadian-sleep-society-on-the-practice-of-daylight-saving-time-dst/.