NEW YORK, July 8: In the coming weeks, Earth is expected to rotate slightly faster than usual, causing several days to be marginally shorter. According to scientists, July 9, July 22, and August 5 will each be between 1.3 and 1.51 milliseconds shorter than the typical 24-hour day due to the moon’s position affecting Earth’s rotation.

A full day on Earth typically lasts around 86,400 seconds, or 24 hours — the time it takes for the planet to complete one full rotation on its axis. However, this rotation is not constant and can be influenced by a variety of factors, including the gravitational pull of the moon and sun, fluctuations in Earth's magnetic field, and changes in the planet's mass distribution.

Historically, Earth's rotation has been gradually slowing down. Scientists estimate that 1 to 2 billion years ago, a single day lasted only about 19 hours. This was likely due to the moon being closer to Earth at the time, exerting a stronger gravitational pull and causing the planet to spin faster. As the moon has slowly moved farther away, Earth’s rotation has decelerated, gradually lengthening days.

In recent years, however, researchers have observed periodic fluctuations. In 2020, Earth experienced some of its fastest rotations on record since modern measurements began in the 1970s. The shortest day ever recorded occurred on July 5, 2024, which was 1.66 milliseconds shorter than 24 hours, according to timeanddate.com.

The expected shorter days in 2025 are linked to the moon reaching its furthest distance from Earth’s equator. This shift alters the gravitational influence on Earth’s spin, much like the change in speed when spinning a top depending on where it's held.

While these changes are part of natural planetary dynamics, scientists have also identified human-driven factors contributing to Earth's changing rotation. NASA researchers have found that between 2000 and 2018, shifts in groundwater and ice — driven by climate change — have lengthened Earth’s days by approximately 1.33 milliseconds per century.

Sudden events can also have an impact. For example, the massive 2011 earthquake in Japan shortened the day by about 1.8 microseconds. Even seasonal changes can affect Earth's spin. According to geophysicist Richard Holme from the University of Liverpool, as trees in the northern hemisphere grow leaves in summer, mass shifts away from the planet's axis, slightly slowing the rotation and lengthening the day.

Despite these shifts, the difference is too small to affect daily life. Our clocks will still show 24 hours, and the change is imperceptible to individuals. Adjustments to time zones only occur when discrepancies between Earth’s rotation and atomic clocks exceed 0.9 seconds. While such a variation has never happened in a single day, over time, the accumulation of these small changes can cause clocks to fall out of sync with Earth’s rotation.

To manage this, the International Earth Rotation and Reference Systems Service (IERS) monitors global timekeeping and introduces “leap seconds” when needed to realign Coordinated Universal Time (UTC) with Earth's rotation.