Meta humbly suggests we all change the way we tell time

The march of time is unrelenting. None of us can escape its ravages or whims. Time is also messy, and while we’d like it to fit neatly into the physical phenomena we use to keep track of it, it’s frustratingly rarely the case. A lot of effort has gone into dealing with it over the years, and now the latest push comes from an unlikely source.

Most of us are familiar with leap years: when a day in February is inserted into the calendar to account for our journey around the sun taking about 365.25 days, rather than even 365. But it’s not just our years. which are not easily expressed in whole numbers, and the length of our days are not precisely 24 hours, either. To explain this discrepancy, Time difference authority International Earth Rotation and Reference Systems Service (IERS) mandates that a leap second be added to our clocks as needed. Unless, of course, Mark Zuckerberg has something to say about it.


The reason we’re talking about the specifics of timekeeping is because Meta wrote a blog post advocating the abolition of the leap second. While his argument has some merit, in typical Facebook fashion, it fails to make it, dismissing the leap second because it “mainly benefits scientists and astronomers,” when in fact astronomers were some of the first. who argued against it.

So why does Meta (and admittedly, other big companies in the industry like Google, Microsoft, and Amazon) want to do away with leap seconds? Why do government agencies like the National Institute of Standards and Technology agree? To understand, let’s start with the big picture and work our way down to the details.

What exactly is a ‘second’?

The Earth revolves around the sun at a speed of about 67,000 mph, and one full revolution is how we define our year. As the entire We whirl around the poles at 1,000 mph (at the equator) and from one complete revolution we determine our days. At the turn of the century, the Muslim scholar Al-Biruni split that day into 24 parts, which he further subdivided sexagesimally (60 parts) into minutes and seconds. So the second was ¹/₈₆,₄₀₀ of a day.

In the 1800s, the need for a standard second arose and scientists realized that the length of a day was not constant — so defining a second as a fraction of a day meant it had no fixed value. A temporary solution was to define the second as a fraction of a year, but in the end it was decided to completely separate the second from the movements of celestial bodies. In 1967, the second was redefined to conform to the atomic properties of cesium (the details of which are beyond the scope of this article) … and this is where our problems begin.

Isidor Rabi and the first cesium atomic clock, NBS-1

Before atomic clocks came on the scene, the world already agreed on Universal Time (UT) as the international time standard. It was based on the prime meridian and the position of the stars. The standard that would become International Atomic Time (TAI) began in 1958 and Coordinated Universal Time (UTC) was adopted in 1960. Although UTC was based on TAI, in order to maintain loose parity with UT, the length of the UTC year (the rate at which the clock ticked) had to be adjusted every year so that the two standards would match each other.

The UTC second was not adjusted to match the TAI second until 1972, at which point it was 10 seconds ahead of UT. In order for UTC to account for the drift between the TAI time and the future UT, it was decided that leap seconds would be added to prevent UTC from drifting too far from the solar-based UT.

I am bored. What does this have to do with computers?

Computers rely on clocks and timers to do all kinds of things. They are also increasingly talking to each other. And to make sure everyone is on the same page, computers rely on the Network Time Protocol (NTP) to ensure their clocks are synchronized with millisecond precision. This synchronization is vital for services such as inventory transactions where the moment of purchase is crucial information. Computers working together also often have to perform a series of actions in a specific order, and they rely on sharing access to the same clock data to make sure this happens.

Leap seconds become a problem because NTP is not a monolith – there are about 3,000 public NTP servers and they don’t always work together. For computers operating on the millisecond scale, the difference of a second is huge and can wreak havoc on systems not designed to handle it.

After the last leap second was added on New Year’s Eve 2016, Cloudflare had a partial outage due to the extra second passing a negative value to a critical function. In the summer of 2012, Reddit was knocked offline for an hour due to the extra second activating all internal timers at the same time, overloading the servers. And in 2015, the New York Stock Exchange postponed the opening pending possible leap seconds.

While the digital ramifications of an extra second in our time matter less every year, that can still be a headache for everyone involved, especially since leap seconds aren’t inserted in a regular interval and they happen only six months before they’re announced. We’ve also only had five since 1999, so plenty of online services have been developed without regard for the leap second. And even when it was justified, there have been only five opportunities to evaluate the impact.

What to do with the leap second?

The problem with UTC as a single universal standard is that it tries to combine the accuracy of atomic time with the variability of solar time. Computers require rigid regularity and thus take advantage of the atomic precision that TAI provides. Humans, on the other hand, are governed by our circadian rhythms and prefer something like UT, which is based on the sun.

A GPS Block III satellite

Meta’s proposed solution to this conundrum is the large-scale abolition of leap seconds. UTC would still be the international standard of time, but it would be separate from the sun, drifting by a second every 800 days. That means sunset will come a minute earlier in 2155 and a full hour earlier in about 8,000 years. While Meta’s plan essentially kicks the can down the road for a few thousand years, the loss of the leap second wouldn’t be felt for long.

Another alternative is to use two time standards. Computers, which require immutable time, could stay on an immutable UTC standard, as Meta suggests. And when it comes to solar time, the leap second could allow us to continue using meat bags without affecting critical digital infrastructure. This wouldn’t be too difficult to implement, as GPS satellites already use their own time standard (which has no leap seconds) and computers have no problem communicating with them.

There have been active talks about removing leap seconds since 2005, but nothing has been decided so far. Any decision should start with the International Telecommunications Union, which is responsible for defining UTC. The last time it was seriously discussed was in 2015, but any decision was postponed to 2023 – which is coming to us soon. Since the US, China and tech giants like Meta, Google, Microsoft and Amazon are all in favor of eliminating the leap second, keep an eye out for a change in UTC in the future, but don’t expect it to impact your day-to-day life. unless Reddit goes down again.

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