Years
and years
The year that we are most familiar with has 365 days, divided into 12 months or just over 52 weeks. The problem with this definition of a year is that it is based on three different time units, derived from different astronomical movements. A day is the time for one rotation of the Earth on its axis. A week is approximately a quarter of a lunar month. A month is approximately one orbit of the Moon around the Earth, while a year is the time taken for the Earth to orbit the Sun. The movements of the Earth, Moon and Sun are not astronomically connected and thus years, months, weeks and days do not relate to each other in whole number quantities as the first indications might suggest. The year
Leap years Let's look at the last 400 years. 1700 was not a leap year, but 1704, 1708 through to 1796 were leap year, 1800 was not made a leap year again and so this pattern continued until the year 2000, which became a leap year because it is divisible by 400. Over 400 years, this evens things up a bit, but the calendar is still about 2.8 hours ahead of the seasons. Although not specifically part of the Gregorian calendar, it has been suggested that the 2.8 hours per 400 years be compensated for by declaring each year divisible by 4 000 a normal year and not a leap year, the next being the year 4 000! What about the 4 hours we are still short of each 4 000 years, I hear you say? I wonder if we will still be using the Gregorian calendar in 2000 years time? Some other years Another motion involving the Earth, is the Solar System revolving around the centre of our Milky Way Galaxy, completing a revolution about every 225 million years. This year is called the Cosmic Year.
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