The clocks go forward on Sunday, March 29, with clocks set from 1am to 2am ET, inaugurating Irish Summer Time and ending Greenwich Mean Time for the season. While many welcome brighter evenings, the switch is more than a calendar quirk: institutional inertia and physiological effects mean the impacts persist well beyond one lost hour of sleep.
Background & context: how the seasonal switch is still set in motion
The seasonal change occurs at 1am, when time moves forward to 2am, marking the start of Irish Summer Time and the end of Greenwich Mean Time for the coming months. Under the current pattern, daylight saving time runs until the final Sunday in October, when clocks are set back an hour. The last Sunday in March and the last Sunday in October are fixed points for the annual cycle.
In 2019 the European Parliament voted to end the seasonal time changes, but EU institutions have not progressed implementation. The European Commission has said it does not plan to submit a new proposal to the Parliament, and Citizens Information states that no changes are expected to summer and winter time in the coming years. The Department of Justice had previously outlined concerns about the prospect of two different time zones on the island of Ireland following the UK’s departure from the EU.
Clocks Go Forward: immediate mechanisms and everyday effects at 1am ET
At the mechanical level the change is simple: clocks displaying 1am should read 2am once the switch is made. For individuals, however, the effect is not limited to a missing hour of sleep. The seasonal shift was historically promoted as a way to make better use of natural light; the idea of summer time was first advanced in 1907 by William Willett to extend evening daylight for outdoor activity.
Today the continuation of uniform timing across member states preserves synchronous schedules for transport, commerce, and cross-border services. That same uniformity also means the population experiences the shift simultaneously, compressing its short-term consequences into the days that follow the change.
Deep analysis: health, safety and the persistence of disruption
The physiological and societal effects of the shift can extend beyond the immediate night it occurs. Dr John O’Neill, molecular biologist and cellular rhythm expert at the Cambridge-based Medical Research Council Laboratory of Molecular Biology, warns of “small but significant” risks tied to the time change. He says: “It does not really serve much of a benefit to anybody these days, whilst exposing us to a small but significant series of risks. It is like everybody in the country gets an hour’s jet lag, all at the same time. “
Dr O’Neill highlights measurable upticks in acute events after the switch: an increase in heart attacks and strokes, and a rise in road traffic accidents for several days following clocks adjustments. He explains that because human physiology anticipates activity at certain times, advancing the clock can leave systems—particularly the cardiovascular system—less prepared to meet earlier demand, elevating risk for older or less healthy individuals.
Regional and global impact: why some countries have walked away
Only about a third of countries currently observe seasonal clock changes, with the practice concentrated in Europe and North America. In the last decade a number of countries have abolished the seasonal shift entirely. Azerbaijan, Iran, Jordan, Namibia, Russia, Samoa, Syria, Turkey, Uruguay, and most of Mexico have stopped changing clocks, a trend documented by the Pew Research Centre. The European Parliament’s 2019 vote and the list of countries that have ended seasonal changes illustrate a broader reevaluation of the policy, even as implementation stalls in the EU.
Retaining a synchronized switch across member states preserves cross-border coordination but leaves open the policy debate: whether the present costs—administrative, health and safety—are justified by the benefits of extended evening light.
Looking ahead: what remains unsettled?
With institutions signalling no imminent legislative change, the cycle of spring-forward and autumn-back will continue for now, but the conversation is not over. As countries choose divergent paths, the pressure between coordination and national preference will persist. Will the ongoing evidence of short-term risks shift policy momentum, or will practical concerns about cross-border timing keep the status quo? For citizens waking on March mornings after the clocks go forward, that question is more than theoretical—it shapes how long the consequences of a single hour will be felt.
