Which is more accurate; a solar based calendar or a lunar based calendar?

Factual Questions
1

My partner and I were doing some reading from a book on Celtic Reconstruction rituals. It’s coming up on the end of the year as based on the old Celtic system; where every year was counted as being 13 moon cycles.

This got me wondering about the accuracy of that type of calendar system and how it compares to the Gregorian, solar based calendar. Which calendar is better for keeping track of the year? I’ve heard various people make comments that the lunar calendar is very accurate. One of my Jewish friends even commented it’s the most accurate calendar system ever devised.

2

The solar is preferred since it tracks the seasons. If you used a lunar calendar with, say, 12 or 13 cycles, the first day of Spring would be different every year. Keeping track of the seasons is particularly important for farming cycles.

The Jewish calendar is lunar based and they have to add a leap month every few years so that things don’t get screwed up.

They are both equally accurate, I guess, but they track different things.

Haj

3

I prefer the calender with the scantily-clad young women that the auto parts store sends me every year.

But…that’s just me.

4

**Hajario wrote:

They are both equally accurate, I guess, but they track different things.**

How are they equally accurate? You mean, over a period of say 10 to 20 years, they’ll still give the same information?

What different things do they track?

5

The lunar calendar is in units of months. Each month is exactly one cycle of the moon. A number of these months (12 or 13) are about equal to a solar year. Some “years” have 12 months and some 13. In 20 years, a lunar month will always start with a new moon.

The solar calendar is in units of solar years, or one trip of the Earth around the Sun. It is arbitrarily divided into 12 luner month like units but only for traditon’s sake. In 20 years, the winter solstace will always be on December 21st. I think a second is subtracted every few years since the Earth’s orbit is slowing down though.

Is that clear? Maybe I don’t understand your question.

Haj

6

That would be lunar, then. Didja get a gander at the moon on Miss September??

7

You might check out: Straight Dope Mailbag: Why do we have leap years? written by an illustrious Straight Dope Staffer.

The question is what you mean by accuracy.

Accuracy depends on what you think is important.

The solar year is “accurate” in the sense that, with minor correction every so many years, it maintains the days of the year in close correspondance with the position of the earth in its orbit, say within a day or so. Thus, March 21 and Sept 21 are always the equinox, to within a day or so error; in the northern hemisphere, August is always midsummer and Christmas is always in winter, etc. The calendar corresponds to the solar year and hence to the seasons.

The lunar calendar is accurate in the sense that it measures the passage of time by the phases of the moon. The phases of the moon come at the same time each month (for instance, full moon is exactly mid-month, etc.)

If you think the phases of the moon are important, then you want a lunar calendar. You note that the solar calendar is flawed, because the full moon falls on a different day each month. If you think the seasons are important, then you want a solar calendar, and you think the lunar calendar is flawed because the holidays aren’t seasonal.

Islam uses a pure lunar calendar, and the days of the year do not correspond to the seasons. One year, Ramadan is in the summer; a few years later, it is in the spring; etc. The lunar year falls short of the solar year by around 11 days (someone will correct me if I’ve misremembered.) The early Muslims were not farmers, and it was not important that holidays fall at certain seasonal times.

The Jewish calendar follows a lunar calendar with adjustments; every so often a full month is added, so that the holidays come out in the right season. The early Israelites were farmers and shepherds, and the Jewish holidays correspond to harvest and planting time in ancient Israel. On the other hand, the new moon was important, and so a calendar was developed that was mostly lunar but adjusted to roughly reflect the seasonal year.

8

Sometimes it’s important to know both the lunar and solar cycles, how else do you know when to old the harvest moon dance? :smiley: Accept that the solar year and lunar month don’t come out to a nice even number of days and you’ll be less frustrated.

9

By definition, a year is one revolution of the Earth around the sun. The moon has nothing to do with what a year is. So a solar calendar will always be more accurate in keeping track of years.

10

Anyone know what the significance of the Gregorian New Year is? It doesn’t fall on a solstice or equinox, or on a day halfway between. Is it based on some earlier holiday, or is it just completely arbitrary?

11

“Of Time And Space And Other Things” by Izaak Asimov

A great book about different ways of keeping time, and specifically differences between a lunar and solar calendar, what the differences are, why, etc.

And maralinn, the whole purpose of this string is that by definition, a year is one revolution of the Earth around the sun by solar year standards! If you live by a lunar year, like millions do and billions have, that is not the definition.

S

12

Thanks one and all for your answers!

**Bosda Di’Chi of Tricor wrote:

I prefer the calender with the scantily-clad young women that the auto parts store sends me every year.**

I keep trying to have the local auto parts store send me calendars of their staff scantily-clad, but they keep ignoring my requests. Discrimination at its worst! :smiley: