Chapter 1: The Ongoing Calendar Challenge

Maintaining our calendars in harmony with the Earth's rotation has always presented difficulties. Any system we devise invariably requires periodic adjustments to stay aligned with actual time. The ancient Julian calendar occasionally necessitated an additional month based on Roman priests' discretion. The Gregorian calendar, which is widely adopted today, adds a day every four years, with three of those leap days omitted every 400-year cycle. The Islamic calendar is reliant on lunar phases and is adjusted as necessary. Nearly all cultures have established systems to keep their calendars aligned with the changing seasons, particularly the equinoxes.

As technology evolved and the demand for precision increased, the necessity for a leap second became apparent. A day is rarely equal to 86,400 seconds. Factors like tidal friction from the Moon, geological shifts that alter the Earth’s mass distribution (such as melting ice caps or earthquakes), and the planet’s inherent cycles contribute to this inconsistency. Consequently, the International Earth Rotation and Reference Systems Service intervenes to add a second to the Coordinated Universal Time (UTC) clock whenever required. Since the introduction of leap seconds in 1972, there have been only 27 additions.

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Section 1.1: The Technical Struggle

Leap seconds present a significant challenge for computer systems. When a leap second is introduced, timestamps must be modified from 23:59:59 -> 00:00:00 to 23:59:59 -> 23:59:60 -> 00:00:00, and not all systems can accommodate this change. The creator of Linux noted, "Almost every time we have a leap second, we find something. It’s really annoying because it’s a classic case of code that is basically never run and thus not tested under normal conditions." Engineers at Meta, the parent company of Facebook and Instagram, indicated that leap seconds could potentially create negative time events, which may disrupt programs and servers. They have pointed out that each leap second has historically been "devastating for the community." For instance, when a leap second was added in 2012, Reddit's servers faced a crash lasting over 30 minutes due to confusion within the Linux subsystem known as "hrtimer." Other organizations, including Gawker and Mozilla, experienced similar disruptions, and serious issues arose for Sun Microsystems and Oracle in 2009.

Subsection 1.1.1: Mitigating the Impact

To alleviate potential complications, many tech companies now implement a strategy known as "leap smear." This approach involves distributing the new leap second over several hours rather than adding it instantaneously. By gradually adjusting their systems’ internal clocks, they can adapt to the new time without encountering awkward timestamps or negative time issues. However, this method is not universally applicable, and some industry leaders express concern that the next anticipated leap second on June 30, 2023, may lead to more complications than solutions, resulting in a growing call to eliminate leap seconds altogether.

Chapter 2: The Potential for a Negative Leap Second

Experts have recently proposed the unprecedented idea of introducing a negative leap second to adjust for the inexplicable lengthening of days. When excluding all known factors influencing day length, there remains no clear explanation for the average day’s increase since 2020. Possible reasons include melting ice caps, La Niña phenomena, volcanic activity, or a 430-day cycle known as the Chandler Wobble. Regardless of the underlying cause, our clocks may soon be misaligned enough to necessitate a negative leap second, compelling tech companies to slow their internal clocks. According to Google, “If a negative leap second were ever to occur, it would be smoothed by accelerating clocks over the 86,399 SI seconds from noon to noon.”

The first video, "How One Second Can Crash the Internet," discusses the potential ramifications of leap seconds on technology and the internet.

While the removal of a mere second may not seem consequential, prominent figures have voiced concerns about its impact on internet infrastructure. Meta warned that “The impact of a negative leap second has never been tested on a large scale; it could have a devastating effect on software reliant on timers or schedulers.” Given that positive leap seconds have already caused issues despite being anticipated six months in advance, a negative leap second—never before attempted—could lead to even greater challenges. Comparisons have been drawn to the Y2K bug that threatened to disrupt society when the century turned, although the actual fallout was minimal.

The second video, "Do We Need a Negative Leap Second?" explores the technical implications and debates surrounding this potential change.

The timeline for implementing a negative leap second remains uncertain. There is a possibility that the movement to abolish both positive and negative leap seconds may gain traction, favoring alternatives like leap minutes or leap hours, which would occur far less frequently. Alternatively, the first negative leap second could be introduced in the next few years without significant incident. However, based on the history of leap seconds, it is conceivable that it could have severe consequences for the internet.