The Earth Is Spinning Faster Than Before — Scientists May Have to Subtract a Second from Global Time for the First Time

The Earth is rotating faster than it used to, and for the first time in history, this could lead to the need to subtract a second from Coordinated Universal Time (UTC), CNN reports, citing data from the International Earth Rotation and Reference Systems Service (IERS) and the U.S. Naval Observatory.

In 2025, scientists recorded abnormally short days. The shortest was July 10, which ended 1.36 milliseconds earlier than the standard 24 hours. July 22 was also shorter than average, and August 5 is expected to follow suit.

The acceleration of Earth’s rotation is attributed to several factors: the gravitational influence of the Moon, seasonal atmospheric changes, and movements in the planet’s liquid inner core. While the difference amounts to only a few milliseconds, it is critical for satellite operations, GPS navigation, communications, financial transactions, and other systems that depend on the precision of atomic clocks.

Since 1972, 27 positive leap seconds have been added to UTC to compensate for the gradual slowing of the Earth’s rotation. However, since 2016, no leap seconds have been required, as the Earth began to speed up. Now, scientists warn that if the trend continues, by 2035 there could be a 40% chance that a negative leap second — removing one second — will be needed. This could cause disruptions in digital systems, similar to the concerns surrounding the Y2K problem when computers transitioned from 1999 to 2000.

Research also indicates that climate change is affecting Earth’s rotation. The melting of glaciers in Greenland and Antarctica redistributes the planet’s mass, which helps offset the acceleration. According to scientists, without this effect, a negative leap second might already be necessary.