When has the United States Senate ever moved faster?

In less than 30 seconds on Tuesday afternoon, lawmakers unanimously consented to make daylight saving time permanent. The legislation never even came up for debate. Senators were apparently cranky enough about losing an hour of sleep last weekend to basically say they had had enough.

In one sense, reform is welcome. Changing clocks twice a year — a policy adopted during the First World War to conserve electricity — is disruptive to people’s sleep and health. It has been associated with a rise in heart attacks, strokes and mood disorders; a spike in morning car crashes; and widespread discomfort, whining and unhappiness. By one estimate, the time shift costs the US economy some $434 million annually.

Sticking with the same time all year, then, would surely make sense. But why choose daylight saving time without a moment’s consideration of the alternative?

Standard time is better aligned with the position of the sun and human nature. It generally synchronises people’s waking with sunrise and bedtime with darkness, in accordance with circadian rhythms. It also enables children and adults to go to school and work in daylight.

DST effectively does the reverse. By increasing exposure to morning darkness and evening light, it shifts body clocks later in the day and makes it difficult to fully wake up or easily fall asleep, a particular hazard for children. Having to be at school or work unnaturally early leads to “social jet lag”, which is associated with a higher risk of obesity, heart disease and depression. As for conserving energy, the original rationale? Studies suggest DST may in fact do the opposite.

Of course, DST has its benefits. Some businesses — such as golf course operators and retail stores — may prefer giving customers an extra hour of sunlight on their way home from work. (Coffee shops might feel differently.) Added daylight also seems to be associated with a decrease in robberies and in evening car crashes. And many people simply prefer the extra afternoon light: in fact, a solid plurality of Americans now say they want to make DST permanent.

Perhaps they don’t remember how unhappy everyone was the last time Congress imposed year-round DST, during the oil embargo of the early 1970s. Although the change was popular at first, late sunrises in the dead of winter soon weighed on people’s minds. Energy savings proved negligible. Stories about children being injured or killed in accidents while walking to school in the dark gained national attention. Support for the initiative plunged by 37 percentage points in just three months. Congress soon reversed course entirely.

It will now fall to House lawmakers to once again determine the fate of daylight saving time. Before repeating a failed experiment, they should slow down and shed some more sunlight on this debate.