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Earth's Days Shrinking: Timekeepers Consider Negative Leap Second

7/10/2025

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Summary

Story summary

Earth's rotation is speeding up, causing days to shrink. On July 9, 2025, expect a day that's 1.3-1.6 milliseconds shorter than usual. This phenomenon, tied to the Moon's gravitational pull, has been noted since 2020. To keep time accurate, global timekeepers might introduce a negative leap second by 2029.

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Story summary

Earth's rotation is speeding up, causing days to shrink. On July 9, 2025, expect a day that's 1.3-1.6 milliseconds shorter than usual. This phenomenon, tied to the Moon's gravitational pull, has been noted since 2020. To keep time accurate, global timekeepers might introduce a negative leap second by 2029.