Retiring the Leap Second
The International Bureau of Weights and Measures (BIPM), which maintains the International System of Units (SI), has voted to expedite the retirement of the leap second, moving forward the date from 2035 to May 20, 2027, an adjustment that could affect computer systems expecting a consistent 60 seconds every minute.
The leap second is occasionally added to Coordinated Universal Time (UTC) to keep it synchronized with the Earth’s rotation. Planet movement fluctuates due to atmospheric, oceanic, core, and lunar forces, creating a 30% probability of requiring a negative leap second by 2035.
Risks to Infrastructure
A positive leap second adds an extra second to the year, which can cause issues for unupdated machines since leap seconds cannot be pre-programmed like leap years. Furthermore, a negative leap second has never been applied before, posing a high risk of anomalies and disruption to unprepared critical infrastructures. The BIPM estimated the required preparation investment to be similar to millennium bug remediation.
Leap seconds have historically caused technical issues, such as website crashes during previous additions. To prevent chaos in national critical infrastructures spanning transportation, energy, telecommunications, and space projects, the standards body opted to scrap leap seconds entirely rather than forcing costly software and hardware upgrades.
The organization notes that this change ensures long-term continuity for UTC, keeping it in sync with TAI for centuries. While large time adjustments can be disruptive, the BIPM points out that shifts of an hour or more are already commonplace globally through time zones and daylight-saving time adjustments.
