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As Earth’s rotation slows, how long will it be before the rules for deciding on leap years have to be revised?
Chris Daniel
Glan Conwy, UK
Leap years are needed because it takes Earth about 6 hours, or a quarter of a day, more than 365 days to complete one orbit round the sun. An extra day in the calendar every four years allows Earth time to catch up with where it should be. If this weren’t done, the seasons would gradually get earlier in the year.
Over a period of 400 years, a total of 96.88 days need to…
