Time change

Twice a year, our bodies have to go through what some scientists describe as “mini-jet lag”: The time change. Read here what effects it has and what tips help.

When the clocks are set forward one hour in spring and back one hour in fall, our biorhythms can get out of sync. 

The changeover to daylight saving time in the spring is particularly difficult because we are robbed of a net hour, which we often chase for days to weeks. Owls in particular, late chronotypes, suffer. They feel longer-lasting after-effects, since the new time corresponds even less to their internal clock than in the case of larks. The consequences can be compared to jet lag. [1] 

Left: With Daylight saving time. Right: Without daylight saving time. The change to and from daylight saving time interrupts the natural progression of sunrise with time. Thus, our physical adaptation to light conditions is disrupted. [1]

Studies have shown that resetting clocks in the fall causes fewer problems [1].  According to experts, this is because most people’s internal clocks lag behind anyway. 


The most common consequences of the time change are fatigue and dejection, which can last for days to weeks in sensitive individuals. Our internal clock determines what our body and brain do at what time of the day. If this is upset, problems can arise that also affect the psyche and bodily functions [2].  For example, several studies have shown that the rate of heart attacks is increased in the days following the daylight saving time change. On the Monday after the time change, according to one study, it was a full 24% higher than in other weeks [3].  Likewise, the number of traffic accidents increases – and sadly, so does the suicide rate [4,5]. While other studies provide less clear results, [6] it seems broadly clear that the time difference has health effects.

Not only that, but our ability to think and concentrate can also be negatively affected by the time change. For example, shortly after the spring changeover, workers tend to engage in more “cyberloafing,” that is, doing things on the Internet in the office other than actual work [7]. A study of U.S. students yielded even more dramatic results: In states where daylight saving time is regularly changed, students perform worse on standardized tests [8].

Zeitgeber checklist for the switch to daylight saving time

How can you best overcome the time change? A few simple actions can make a big difference. The following guide tells you how to master the time change weekend by moving your internal clock forward with you. 



In general, it should be said that one’s routines should be adapted to the new time as slowly as possible. The earlier they start to move their bedtime forward, the easier the changeover will be.


If you experience a strong reaction to the time change, you should drive less and avoid dangerous activities for the first few days. The increased likelihood of accidents during these days can be avoided in this way.

Why all this?


Why politicians once decided on daylight saving time is in its English name: To extend the time of daylight and thus ultimately save energy. In 1996, the EU standardized daylight saving time so that all member states now set their clocks forward on the last Sunday in March and back on the last Sunday in October. In total, around 70 states are trying to save energy through these measures. But even this main reason for daylight saving time has become controversial: The German Federal Environment Agency found that the energy-saving effect is cancelled out by the heating now required in the early morning hours [9]. Many researchers therefore advocate the abolition of daylight saving time. This 2018 EU-wide was brought into focus by an online survey: 84% of the approximately 4.6 million responses were in favor of abolition. The EU reacted with the decision to carry out the time changeover for the last time in 2021 and to leave it up to the countries themselves to decide whether they want to continue living in normal or summer time [10]. Thus, in March and October 2021, respectively, the clocks would have been turned for the last time. However, some governments, such as Germany, insist on a prior investigation by the European Commission. An impact assessment is indispensable before such a far-reaching decision. However, the Commission refuses to provide it. Thus, it will probably be some time before our clocks are changed for the last time. [11]


[1] Thomas Kantermann, Myriam Juda, Martha Merrow, Till Roenneberg; The Human Circadian Clock’s Seasonal Adjustment Is Disrupted by Daylight Saving Time; Current Biology, Volume 17, Issue 22, 2007, Pages 1996-2000, ISSN 0960-9822, https://doi.org/10.1016/j.cub.2007.10.025.

[2] Manfredini R, Fabbian F, Cappadona R, Modesti PA. Daylight saving time, circadian rhythms, and cardiovascular health. Intern Emerg Med. 2018;13(5):641-646. doi:10.1007/s11739-018-1900-4

[3]  Sandhu ASeth MGurm HS; Daylight savings time and myocardial infarction, Open Heart 2014;1:e000019. doi:10.1136/openhrt-2013-000019

[4] A Chronobiological Evaluation of the Acute Effects of Daylight Saving Time on Traffic Accident Risk; Fritz, Josef et al.;Current Biology, Volume 30, Issue 4, 729 – 735.e2

[5] Berk, MichaelDodd, SeetalHallam, KarenBerk, LGleeson, John and Henry, M (2008) Small shifts in diurnal rhythms are associated with an increase in suicide: The effect of daylight saving. Sleep and Biological Rhythms, 6 (1). pp. 22-25. ISSN 1446-9235

[6] Arthur Huang, David Levinson; The effects of daylight saving time on vehicle crashes in Minnesota; Journal of Safety Research, Volume 41, Issue 6, 2010, Pages 513-520, ISSN 0022-4375, https://doi.org/10.1016/j.jsr.2010.10.006.

[7] Wagner, D. T., Barnes, C. M., Lim, V. K. G., & Ferris, D. L. (2012). Lost sleep and cyberloafing: Evidence from the laboratory and a daylight saving time quasi-experiment. Journal of Applied Psychology, 97(5), 1068–1076. https://doi.org/10.1037/a0027557

[8] Gaski, J. F., & Sagarin, J. (2011). Detrimental effects of daylight-saving time on SAT scores. Journal of Neuroscience, Psychology, and Economics, 4(1), 44–53. https://doi.org/10.1037/a0020118

[9] https://www.umweltbundesamt.de/sites/default/files/medien/publikation/long/3535.pdf


[11] WAZ. https://www.waz.de/politik/eu-der-bizarre-streit-um-das-ende-der-zeitumstellung-id231854187.html