Daylight Saving Time Explained
The practice of advancing clocks during warmer months to extend evening daylight—loved by some, loathed by others, and increasingly being reconsidered.
2024 DST Dates
| Region | Spring → | Fall ← |
|---|---|---|
| USA & Canada | March 10, 2024 | November 3, 2024 |
| Europe (EU) | March 31, 2024 | October 27, 2024 |
| Australia | October 6, 2024 | April 7, 2024 |
| New Zealand | September 29, 2024 | April 7, 2024 |
2025 DST Dates
| Region | Spring → | Fall ← |
|---|---|---|
| USA & Canada | March 9, 2025 | November 2, 2025 |
| Europe (EU) | March 30, 2025 | October 26, 2025 |
| Australia | October 5, 2025 | April 6, 2025 |
| New Zealand | September 28, 2025 | April 6, 2025 |
A Brief History of DST
The concept of adjusting clocks seasonally was first proposed by Benjamin Franklin in 1784, though mostly in jest. The modern idea was seriously proposed by New Zealand entomologist George Hudson in 1895, who wanted more after-work daylight for bug collecting.
Germany was the first country to implement DST in 1916 during World War I to conserve coal. Other nations quickly followed, including the UK and USA. The practice has been adopted, dropped, and re-adopted many times since, often during wars and energy crises.
Today, approximately 70 countries observe some form of daylight saving time, though this number is shrinking as more regions question its modern relevance.
Countries With DST
Countries Without DST
Arguments For and Against DST
👍 Arguments For DST
- More evening daylight for outdoor activities and commerce
- Potential reduction in crime during evening hours
- Minor energy savings (though disputed by modern studies)
- Boost to retail, sports, and tourism industries
👎 Arguments Against DST
- Health impacts: increased heart attacks, strokes after spring change
- Disruption to circadian rhythms and sleep patterns
- Complex software bugs and scheduling issues globally
- Modern energy savings are negligible (increased A/C use)
DST Is Changing Worldwide
Tips for Developers
- 1.Always store timestamps in UTC — convert to local time only for display
- 2.Use timezone-aware libraries like date-fns-tz, Luxon, or Day.js with timezone plugin
- 3.Reference IANA timezone database (e.g., "America/New_York", not "EST")
- 4.Test edge cases — the hour that "doesn't exist" (spring) and the hour that "repeats" (fall)
- 5.Keep timezone data updated — rules change more often than you'd expect