400-year Leap Years
I heard on
the radio it will be 400 years before we have another leap year like this one.
Is that true? (Jeannine, Albuquerque, NM)
It is true. According to the Royal Greenwich Observatory, the calendar year is 365 days
long, unless the year is exactly divisible by four, then an extra day is added to February so
the year is 366 days long. If the year is the last year of a century, e.g., 2000, 2100, 2200,
2300, 2400, then it is only a leap year if it is exactly divisible by 400. So, 2100 won't be a
leap year but 2000 is. The next century year, exactly divisible by 400, won't occur until
2400--400 years away.
These rules make the average length of the calendar year the same as the length of the
Earth's orbit around the Sun, so that the seasons always occur during the same months
each year. Otherwise, the first day of Spring, by the calendar, could happen when the days
are shortest and winter has enwrapped the land--a bad time for planting. |
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