The formula for calculating whether a year is a leap year or not is as follows: if a year can be evenly divided by 4 (such as 2012), then it is a leap year unless it can also be evenly divided by 100 (such as 2100). There is one further exception: if a year can be evenly divided by 400 (such as 2000), then it is a leap year.
Know MoreA day on Earth does not really last 24 hours. It takes 23 hours, 56 minutes and 4.1 seconds for the Earth to make a complete rotation. Because of this, the Earth actually rotates about 365.24 times per year. Adding an extra day every four years helps to synchronize the calendar year with the solar year. If the discrepancy were exactly one quarter of a year, then every four years would be a leap year without variation. Since the difference is 0.24 instead of 0.25, one leap year is skipped three times out of every 400 years. Leap year originated in the 16th century, when people realized that the vernal equinox was falling on March 11 instead of March 21. Pope Gregory XIII adjusted the calendar by moving the date ahead by 11 days and instituted the practice of adding an extra day to the calendar every four years.
Learn MoreCalendar dates repeat regularly every 28 years, but they also repeat at 5-year and 6-year intervals, depending on when a leap year occurs within those cycles, according to an article from the Sydney Observatory. Repeating calendar dates are also affected by the adjustments made for leap years at the end of each century.
Full Answer >A leap year has 366 days instead of 365 days. The addition of this extra day to the Gregorian calendar occurs in the month of February.
Full Answer >There are 20 years in a score. The word "score" can be used to mean a set or group of any 20 items, not just years.
Full Answer >The transit of Venus happens every 100 years. The last one was in June 2012, and the next one occurs in 2117. This happens as Venus directly passes between the Earth and the Sun. This once-in-a-lifetime astronomical alignment has been witnessed eight times since the telescope was invented. These eye-witness-accounts occurred in 1631, 1639, 1761, 1769, 1874, 1882 and 2004, and the last was in June 2012.
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