In A Leap Year Should We Replace Leap Seconds With Leap Minutes?

This year, as every fourth year since 1904, the world will add an extra day on February 29, making 2024 a leap year. While that is generally accepted, debate is growing about whether we should keep adding the occasional leap second. It might seem like an arcane question of little relevance to most people, but with the Russian government firmly taking one side of the debate, things may not go smoothly. It’s not a likely cause for World War III, but we could still be hearing more about this soon, with several solutions under consideration.

One proposal, promoted by Dr Judah Levine of the Time and Frequency Division at the National Institute of Standards and Technology, is to move from frequent leap seconds to rare leap minutes. To understand the reasoning, however, it’s worth reviewing why our clocks don’t always move smoothly.

Why The Leap Year?

The length of the day and year makes an argument against an intelligently designed universe. Instead of the time the Earth goes around the Sun being divisible exactly by the number of times it turns on its axis, we get 365.2422 days to a year. If we insisted on keeping every year to 365 days our calendar would get out of step with the seasons. People at high northern latitudes might miss snow on Christmas Day, but historically a bigger problem would have been confusion about when to plant crops.

That problem was largely solved through the introduction of a leap year every four years. When that proved insufficiently precise, the Gregorian Calendar was introduced. This skipped a leap year three centuries out of four. That makes the average year length so close to the true length our seasons are safe for many thousands of years to come. What was controversial about the Gregorian Calendar was making it retrospective, moving the date forward 10 days. Some say riots broke out because in a more superstitious time, people thought their life would be shortened to match, although this may be a myth

The banner in the back right reads “Give us back our 11 days”. This painting contributed to the belief there were riots when England caught up with the Gregorian calendar adopted in Catholic countries a century before.
Painting by William Hogarth, public domain.

Shorter Leaps in Time

There’s a mismatch in the naming of leaps. We don’t add a whole year on February 29, but we talk about leap years, not leap days. Yet when a second is added to the calendar, we call it a leap second, not the slightly extended period in which it belongs a leap hour.

That pedantry aside, the leap second, and potentially negative leap second, were introduced to deal with a different problem; the fact the Earth’s rotation is not perfectly stable. Our days are growing longer, thanks mainly to interactions with the Moon. If we don’t make adjustments of some sort we could end up with the Sun rising at midnight and other deeply disruptive events. Certainly, it will take us an awfully long time to get to that point. Nevertheless, with a concern about addressing problems early humanity has notably failed to show on other matters, leap seconds have become a regular part of the calendar.

Since 1972 every few years a second has been added at midnight either on June 30 or December 31 to keep things in balance. Clocks precise enough for this to matter get adjusted. We even have an international body to ensure the nations of the Earth are all on the same page in this matter, an example of cooperation again sadly lacking elsewhere on many more urgent matters. 

Goodbye, leap second, hello, leap minute?

Now, however, there is dissension in the ranks. In 2022 the International Bureau of Weights and Measures (BIPM) voted to abolish the leap second – not immediately but by 2035. It was all very well to throw seconds in when the number of devices keeping such exact time was few, but now computers worldwide have to cope with regular readjustments, and some don’t like it.

This is where Levine comes in. As one of the select group of people paid to think about these things, he notes that most people’s lives won’t be affected if the Sun crosses the meridian a few seconds away from noon. After all, we live in broad time zones where clock time only matches the position of the Sun precisely along a single line of longitude.  

“Having to deal with leap seconds drives me crazy,” Levine told the New York Times in the lead-up to the World Radio Conference in Dubai last year to consider such things. “We all need to relax a little bit.”

Therefore, Levine suggests, we should let the seconds build up, the heavens getting ever so slightly behind clock time, until we’re behind enough to add a whole minute in. The few people who need their clocks to match the sky perfectly are those best positioned to make adjustments to official time.

There are a lot of advantages to this – people might even hold parties to celebrate the leap minute; leap seconds are too common to bother with.

Nevertheless, the conference failed to adopt Levine’s idea, in part because the leap second now has considerable inertia. An odd alliance is against change, including the Catholic Church and the British and Russian Governments. Their motives vary, but all favor the current system.

Attachment to tradition seems to motivate some, but it’s been reported that Russian satellites are designed around leap seconds. If so, a change may be more than a simple matter of reprogramming. There’s speculation abandoning the leap second could affect Russian military systems, but if so, don’t expect them to admit it.

That makes achieving change very difficult. It’s one thing to convince the Vatican that abandoning the leap second does not disconnect humanity from the cosmos. After all, it came around to Galileo eventually. It’s much harder to change the mind of a nuclear power who won’t even acknowledge their true reasons. Don’t expect riots over stolen time, but don’t book the leap minute party just yet.

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