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The different calendars
by universal sea
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x universal sea   - at 2:10 am on Friday April 2 2004 x
x How some of the common calendars differ, and why they do x
x universal sea earth moon sun Singapore - It would be better if you read this before carrying on with the rest that's here.

After we do all that gangbang with the Earth and the Sun, let's make it a little more complicated... bring on the moon.

The moon revloves around the Earth in a cycle which lasts roughly 29.5 days. A very common misconception is that whenever the moon passes between the Earth and the Sun, a solar eclipse occurs - this is not true, or else we would be having solar eclipses every month. In Singapore we'd get that maybe once every 400 years. In order for a solar eclipse to occur, the moon must be in a very special position, so precise that it blocks the rays of sun from reaching the Earth. Most of the time, it blocks a small fraction of the rays, and this causes what is called the 'new moon'.

Picture this: three objects stand in a line, the Sun, folled by the moon, then the Earth. The moon will block maybe 5% of the Sun's rays at that instant. It is common knowledge that the moon possess no internal source of light energy, what we see is merely the reflection of the Sun's rays. So, if the moon happens to be blocking part of the Sun's rays, we in fact, would see nothing at night. The face of the moon facing us gets hit with no light, and hence we cannot see it.

The second senario is of course when the Sun, the Earth, and the Moon are lined up in that order. In this case, the face of the moon which is facing the Earth is also facing the sun, meaning that we see the whole face - the full moon.

Now that we've gotten the crazy cycles out of the way, here's how the various calendars differ. Firstly, though, there are a few terms to note:

The syndonic month is the period of time from one new moon to the next. As mentioned earlier, it lasts about 29.5 days.

The tropical year os the period from one equinox on the North Pole to another. It lasts about 365 days.

Onto the various calendars...

Firstly, we have the Solar (or Gregorian) calendar, the basic unit of which is the day. Since, to be accurate, the tropical year lasts 365.4 days, the solar calendar approximates the tropical year by adding a day every leap year (or else in one hundred years' time we'd be 25 days behind). This calendar is based completely on the Earth's revolution around the sun, and ignores the moon. It lasts 365 / 366 days.

By the way, if you're interested, a leap year is a year which is divisible by 400 but not a hundred, OR if the year is divisible by 400. (2004 is divisible by 4 but not 100 and therefore is a leap year).

Next, we have the Lunar calendar. This, contrary to popular belief is not the Chinese calendar. Rather, it is the Islamic calendar. This calendar completely ignores the sun and is based on the moon. The basic unit of this calendar, as opposed to the day, is the lunar month. One lunar year consists of 12 lunar months, and therefore lasts roughly 29.5 x 12 = 354 days. Note that one lunar year is about 11 days shorter than a solar year. The year can be 353 or 355 days.

This accounts for the fact that Hari Raya Puasa and Hari Raya Haji can fall any day of the solar year. You take the HRP of one year, subtract 11 days from the date it falls, and you will get the HRP of the following year. Once in a while, like the year 2000, you will get two HRPs in the same year.

Btw, since Ramadan (month in which Muslims must fast) can fall any time of the year, this does not mean that the Muslims in countries where there is the midnight sun cannot eat at all, instead, they follow the time in Mecca. In places like Singapore, however, they still start fasting at dawn and break fast at dusk.

Finally, on to the most complicated of the three, is what is known as the Chinese calendar, the lunisolar calendar. As with the lunar calendar, the basic unit of this calendar is the lunar month. This calendar tries to combine the both the solar and lunar calendars, hence the name. It approximates the solar calendar by adding leap months. This is mainly due to the fact that Chinese New Year must always fall within a certain period - Jan 21 to Feb 21 of the solar calendar, and therefore, a lunisolar calendar can have either 12 or 13 months. If it is found that CNY is falling too early on a certain year, a leap month is added to that year so that CNY falls within the stipulated time frame. A 12-month year will last 254 (sometimes 353/355) days. A 13-month year will last between 383 and 385 days.

As a general rule of thumb, if you want to impress your friends, the way to calculate the date of the next CNY (plus minus one day), is to subtract 11 days from the date of Chinese New Year in the year you are currently in. If subtracting 11 brings you past Jan 21, then you add 19 to the date instead. You will generally be right, but due to the inaccuracies with the length of the year, you may be a day off, but never more.

I don't know much about the other calendars, but I found these things pretty interesting a while ago...
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x Unread post xjj_4487   - at 2:11 am on Friday April 2 2004 x
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x jj_4487 Haha whoops.. there you have another of my legendary typos..
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