Calendars more than just days and months

by David Malcolm

wikipedia.org

The Chinese calendar and the Islamic calendar seem strange to those of us who have been brought up in the West.

There is something seemingly strange with New Year coming at the end of January (or a few days before, or a couple of weeks after); or the month of Ramadan falling earlier and earlier each year. One may ask: How are the Muslims supposed to know when to plant their crops? If some date on their calendar is chosen, before very many years it will be completely out of tune with the seasons. The unfamiliar features of the Islamic calendar can be accounted for on the basis that it is a lunar calendar which means a month is very accurately tied to the phases of the moon.

The moon proceeds through its phases in a cycle of about 29.5 days (called the ‘synodic’ month), so having months alternating between 29 and 30 days keeps closely in step with the moon.

A new moon signals a new month and a full moon the middle of the month. This idea is not foreign to our western culture. The Shorter Oxford dictionary notes that the word ‘month’ is derived from the word ‘moon’. The primary definition of month is given as “a measure of time corresponding to the period of revolution of the moon”. So the idea of a lunar month is logical. On the Islamic calendar a sequence of 12 of these lunar months make up a year.

The Chinese calendar is more complicated. It is often popularly referred to as a lunar calendar, but is actually a luni-solar calendar.

It has months which are tied in with the phases of the moon as does the Islamic calendar, but additionally it keeps the year in step with the seasons in the long term by having some years with 13 months. Again that seems strange to us. Surely there should be 12 months in a year?

Is there no certain rule by which calendars ought to be formulated? Some yardstick to provide the various ethnic groups with a basis for designing our calendar? Do we not have some absolute standard that will enable us to say that some calendar features are unacceptable?

In fact, we do have such a yardstick. The Bible sets out God’s provisions:

And God said, “Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, and let them be lights in the expanse of the heavens to give light upon the earth.” And it was so. And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. And God set them in the expanse of the heavens to give light on the earth, to rule over the day and over the night, and to separate the light from the darkness. And God saw that it was good. And there was evening and there was morning, the fourth day. (Genesis 1:14-19)

So God’s word tells us that He provided the astronomical cycles for us to determine time periods (seasons).

The day-night cycle, caused by the earth’s rotation defines the day for us; the phases of the moon give us the month; and the motion of the stars, moving full circle over about 365 days sets the year for us. And there is no requirement here for there to be 12 months in a year.

No calendar conforms with God’s provision, and it comes as a bit of a shock to realise that the Roman calendar likewise falls short.

That calendar we are all familiar with—that was adopted by the early church and has become the standard world-wide—is deficient. In fact, just as the Islamic calendar is defective because it has a year arbitrarily made up of 12 lunar months, so the Roman calendar is defective because it has a month which is just an arbitrary division of the year into 12.

The Hebrew calendar has been used by the Jewish people for many centuries, and is still in use today. Like the Chinese calendar, it has months alternating (generally) between 29 and 30 days, to keep in step with the lunar month, and also keeps in step with the solar year in the long term. It has a fixed cycle containing seven 13-month years in every 19 years. (See comparison table).

The week

We have seen that the day, the month and the year had their origins in astronomical periods, which God instituted for that purpose. But the week is different. It is not based on any observable astronomical period. The origin of the seven-day week is set out in Genesis when God completed His creation, setting a pattern for His creatures (Genesis 2:2-3 and Exodus 20:11).

Twelve months

It would seem there is no mandate for the year to consist of 12 months. Yet various people groups have gone away with the idea that there should be 12 months in the year. Why?

It is tempting to wonder if originally there were exactly 12 lunar months in a solar year. Perhaps, in the way God set things up in His perfect creation, there were exactly 30 days in a lunar month and exactly 360 days in a solar year. Various people groups could then have a valid cultural memory, handed down from the time before different languages arose at the tower of Babel and people were dispersed.

There are some indications of this mathematically perfect scheme:

• The symbol we use for a degree (an elevated circle) apparently came from the Babylonian mathematicians and is intended to represent the sun. With 360 days in a year, the sun would move exactly one degree per day (Observed by a motion of the stars in one night).
• In Hebrew terminology, a month with only 29 days is called ‘defective’. Normally a month has 30 days.
• The chronology of the global flood in Genesis chapters 6 to 9 seems to allow for 370 days, but the starting and ending dates indicate clearly it was a year plus 10 days (Genesis 7:11-13 says the “fountains of the great deep burst forth, and the windows of the heavens were opened” on 17^th day of the second month when Noah was 600 years old, while Genesis 8:13-16 says Noah and his family came out of the ark on the 27^th day of the second month in Noah’s 601^st year).

However, the idea is hard to substantiate when the physics are considered.

The earth could have increased its speed of rotation to get an extra five-and-a-bit days in a year (for example, through catastrophic plate tectonic movements¹ decreasing the moment of inertia of the earth at the time of the Flood), and the moon could have been moved closer to the earth to get an increased number of lunar months in a year, although no particular mechanism has been identified.

Measuring seasons and days and years

All the pointers are there in Genesis—in God’s perfect creation—for humans to order their lives starting with a 24-hour day. God gave us a pattern for working six days and resting on the seventh.

He gave us the stars by which we can even navigate our way around the earth. And He made an orderly universe so that by using the intelligence that comes from the Creator, we can observe, for example, that the earth revolves around the sun once a year. And that the earth also rotates on its axis every 24 hours.²

And, using that knowledge of astronomy, the ancients were able to work out the earth’s position in the universe.

Days, months, years and seasons have always been central to our existence and a calendar a vital tool to keep track of events in our lives. So when you next flick through a calendar—even our flawed one—it should remind you of God’s creative genius and that it was He Who set time and our world in motion in six, literal, 24-hour days, about 6,000 years ago.

Comparison of Calendars

Problems with the Roman Calendar

• The months on our calendar bear no relation to the phases of the moon. This is a serious problem but it is not the only problem.
• Most months (seven) have 31 days and only a minority (five) have 30 days or less. A total of 365 days could be obtained with seven months of 30 days and five months of 31, and six of each in a leap year. Why is the distribution so illogical?
• Four of our months have names in Latin that designate a number: September, October, November and December mean literally 7^th, 8^th, 9^th and 10^th. But they fall two months later. Presumably, at one time the year began with March, which would explain why poor old February (coming at the end of the year) just gets whatever days happen to be left over.

The Chinese Calendar

Some years contain 13 months (instead of the usual 12) in order to ensure that New Year occurs as close as possible to when the constellations are in a fixed position in the night sky. Months always coincide with the phases of the moon.

Table of workings

This is the author’s calculations for the Chinese calendar from the published dates.