We also call leap year the bissextile year. 　2　In our calendar system there is a need for a leap year because the solar year(the time it takes the earth to go around the sun once)is actually slightly more than 365 days long. That extra day—Feb. 29 every four years—helps correct the difference between our calendar and the solar calendar.

　　It is said that leap year was first made part of the calendar by the ancient Roman leader Julius Caesar. His astronomers had calculated the length of the solar year to be 365 days and six hours. So Caesar declared that an extra day be added to the calendar. 　3　However, Caesar’s adjustment was not completely accurate because his astronomers’ year exceeded the true solar year by eleven minutes and fourteen seconds. By 1582, a difference of ten days had developed between the calendar year and the true solar year. To correct this error, Pope GregoryⅩⅢ ruled that every fourth year would continue to be a leap year except for century years that could not be divided evenly by 400. By this system, century years such as 100, 1800, and 1900 were not leap years, but the year 2000 was a leap year. 　4　

　　People born on Feb. 29 celebrate their growing up a little differently from the rest of us.

　　　5　But if they go strictly by the calendar, they have only one-fourth as many birthday celebrations as most people.

　　A. They acknowledge that they get older each year.

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