国际度量衡局（BIPM）宣布将于 2027 年 5 月 20 日世界计量日正式废除「闰秒」制度，终结了计量学界长达三十年的争论。自 1972 年以来，为了弥合原子钟推动的协调世界时（UTC）与受月球潮汐摩擦、地核、海洋及大气影响而变慢的地球自转天文时间（UT1）之间的差距，全球共计增加了 32 个闰秒，最近一次是在 2016 年。

尽管闰秒有助于让原子时间与天文时间保持同步，但对依赖 UTC 运作的众多现代科技基础设施、API 与资料库而言，每隔几年调整一次闰秒却带来了巨大的混乱与系统故障风险。例如澳洲航空（Qantas）的订位系统曾在 2012 年因闰秒而瘫痪，而 Google 与 Meta 等科技巨头则不得不采用「涂抹（smear）」技术，将多出的一秒钟拆分成极小增量分摊在一整天内消化。

促成当局决定在 2027 年废除闰秒的关键原因，是气候变迁导致冰川融化、改变了地球重力分布，使地球自转速度近年来反而加快，进而可能在 2029 年引发史上首次从未经过测试且风险极高的「负闰秒」。废除闰秒后，各系统只需维持每分钟 60 秒的正常运作，而针对原子时间与天文时间未来的持续偏离，BIPM 已同意改采数千年后才会累积到的「闰小时」机制留待后代处理。

The International Bureau of Weights and Measurements (BIPM) announced that it will officially abolish the leap second on May 20, 2027, World Metrology Day, ending a three-decade debate in the metrological community. Since 1972, 32 leap seconds have been added—most recently in 2016—to keep atomic-clock-driven Coordinated Universal Time (UTC) aligned with astronomically kept Universal Time (UT1), which slows down due to tidal friction with the moon as well as the effects of Earth's molten core, oceans, and atmosphere.

Although leap seconds kept atomic and astronomical time synchronized, adding them every few years wreaked havoc on modern technological infrastructure, APIs, and databases that rely on UTC. For instance, the airline Qantas suffered a booking system failure in 2012 due to a leap second, while major tech companies like Google and Meta had to resort to a "smear" method that spreads the extra second in tiny increments over the course of a day.

A decisive factor in ending the leap second in 2027 was the rising probability of the world's first "negative leap second" as soon as 2029, driven by climate change melting ice, shifting Earth's gravity, and speeding up the planet's rotation—posing untested and severe risks of system failures. With the demise of the leap second, systems can simply continue accumulating normal 60-second minutes, while the ongoing drift between atomic and astronomical time will eventually be addressed by a "leap hour" millennia in the future.