Calendars (Ancient and Modern)

A calendar is a system that shows when each year begins, how long it lasts, and how it is divided into days, weeks, and months.

People rarely think about how the modern calendar works. However, without a calendar, it would be very difficult to create a clear timeline of events. A timeline shows the order in which events happened. It would also be impossible to predict the changing seasons accurately.

Before the calendar reached its modern form, it went through several stages of development.

Days and Their Divisions

Astronomy and the Calendar

Jewish Calendar

Jewish Festivals

Conclusion

The earliest way to measure time was probably to count days. Later, people divided each day into smaller parts. These parts eventually became the 24 equal periods called hours.

The Sumerians seem to have developed the system of measuring time in days, hours, and minutes. They also used the word “day” in a narrower sense to mean a 12-hour period.

The stairway built by King Ahaz was used to tell time by the movement of a shadow (2 Kings 20:9; Isaiah 38:8). However, people probably did not measure hours precisely until much later.

The ancient Egyptians began the day at dawn. They divided the day into two periods of 12 hours. In the second century AD, the Egyptian astronomer Ptolemy and his followers developed a system that began each day at noon. At noon, the sun is at its highest point in the sky.

The Roman day began at sunrise and had two parts. The second part of the day began at sunset.

Ancient peoples created calendars by observing the repeated movements of the sun and moon. A solar year is the time the earth takes to travel once around the sun.

Ancient peoples depended on the changing seasons. Their lives were shaped by changes in temperature and by the different lengths of day and night during the year.

The seasons occur because the earth travels around the sun while also turning on its axis. The earth’s axis is tilted at an angle.

In the Northern Hemisphere, the longest day of the year is called the summer solstice. It occurs around 21 June. The winter solstice occurs on 21 or 22 December. On that day, the sun appears lowest in the sky at noon, and the daylight hours are shortest.

In the Southern Hemisphere, the seasons are reversed because of the earth’s tilt.

The spring and autumn equinoxes fall between the solstices. The spring equinox occurs around 21 March, and the autumn equinox occurs around 23 September. At these times, the sun is directly above the equator, and day and night are about equal in length. The word “equinox” comes from Latin words meaning “equal night.” Ancient peoples could measure a solar year as the time between two matching solstices or two matching equinoxes.

A solar calendar measures days by observing the time between two returns of the sun to the same position in the sky. This may be from one sunrise to the next, from one sunset to the next, or from one midday to the next. A day is the time the earth takes to turn once on its axis. It is now divided into 24 hours.

However, the earth’s daily rotation does not match its yearly journey around the sun exactly. A solar year is not a whole number of days. It lasts 365 days plus part of another day. This difference creates problems when making a calendar.

The greatest calendar problems appear when both the sun and moon are used to measure the year. Ancient peoples found it difficult to make the solar year match the lunar cycle. This was especially difficult when months were based on the changing phases of the moon. The problem occurs because the moon travels around the earth while the earth travels around the sun and turns on its own axis. These different movements do not fit together exactly, so they create many calendar difficulties.

A lunar calendar measures time by lunations. A lunation is the length of time between one new moon and the next. Each lunar month begins when the thin crescent of the new moon first becomes visible at sunset. A lunar month lasts an average of a little more than 29 and a half days.

The moon travels around the earth in about 27 and one-third days. However, during that time, the earth also moves around the sun. Because of this movement, the moon needs about two more days to return to the same position between the earth and the sun and produce another new moon.

A lunar year has 12 months and is about 11 days shorter than a solar year. To correct this difference, some calendar systems added extra days or months. This practice is called intercalation.

The ancient Chinese calendar had 12 months of either 29 or 30 days. It added an extra month every 30 years. The Muslim lunar calendar is still used throughout Islam. It also works on a 30-year cycle. The second year of each cycle is a leap year. After that, a leap year occurs every three years. A leap year has 355 days, while an ordinary Muslim year has 354 days. The ancient Hebrew calendar had the same basic problems as other lunar calendars.

The lives of the people of ancient Israel were closely connected to the calendar. The calendar helped organize many parts of their religious and daily life.

The Jewish calendar begins with the traditional date of creation. This date is set at 3,760 years and three months before the Christian era (the years counted from the birth of Christ). To estimate the Jewish calendar year, add 3,759 to the year in the Gregorian calendar (the calendar used in most of the world today).

However, this method does not give an exact result for every month. The Jewish civil year begins in autumn (September or October), while the Gregorian year begins in midwinter (January).

The Jews adopted most of the 12 month names from the Babylonians after the exile. These months do not match the months of the Roman calendar exactly. Instead, they overlap with them.

The Old Testament mentions the names of more than half of these months:

Chislev (Nehemiah 1:1; Zechariah 7:1)

Tebeth (Esther 2:16)

Shebat (Zechariah 1:7)

Adar (Esther 3:7; 8:12)

Nisan (Nehemiah 2:1; Esther 3:7)

Sivan (Esther 8:9)

Elul (Nehemiah 6:15)

The Jewish month always began with the new moon, about every 29 and a half days. For this reason, the Jewish year had 354 days. This was a lunar calendar, a calendar based on the cycles of the moon. A solar year is based on the earth’s movement around the sun. We do not know exactly how the Jews first adjusted their lunar calendar to match the solar year.

Later in Israel’s history, an extra month was added between Adar and Nisan. This month was sometimes called Veader (“second Adar”). It was added seven times during a 19-year cycle. When this happened, Adar also received an extra half day.

The Jewish month names used today come from the period after the Jews returned from Babylonia to Palestine. Before the Babylonian exile, at least four other month names were used:

Abib (Exodus 13:4) later became Nisan,

Ziv (1 Kings 6:1, 37) became Iyyar,

Ethanim (1 Kings 8:2) became Tishri, and

Bul (1 Kings 6:38) became Heshvan, originally called Marcheshvan.

The earlier month names were connected with farming. For example, Abib was the month when the heads of grain became ripe. Ziv was the month when flowers bloomed in the desert.

This connection with farming also appears in what seems to be the oldest known Hebrew calendar. It was found at Gezer, southeast of Tel Aviv, in 1908 and dates to the tenth century BC. The calendar was probably written by an Israelite schoolboy. It divides the year according to farming activities such as planting, harvesting, pruning, and storing crops.

The months were especially important for Jewish religious life. They helped the Jewish people remember important events in their history. The beginning of each month was considered holy.

For ancient Israel, the moon became a spiritual symbol of the nation. The sun later became a symbol of the Messiah (Malachi 4:2). The moon does not produce its own light, so this symbolism was especially meaningful. Israel was to reflect the Messiah’s light to the world.

The Jewish calendar remained unchanged during the approximately 400 years between the Old Testament and the New Testament. This was true even though Greek rulers tried to introduce a different lunar calendar, probably based on a Macedonian system.

In that calendar, each of the 12 months had 30 days, and five days were added to the final month of the year. Even with these extra days, the calendar only came close to matching the solar year.

A Hebrew month usually began around the middle of a month in the modern calendar. People planted crops in November and December and harvested them in March and April.

Month

Today’s Calendar

Bible Reference

Israel’s Festivals

1 Nisan (Abib)

March–April

Exodus 13:4; 23:15; 34:18; Deuteronomy 16:1

Passover (Leviticus 23:5) Unleavened Bread (Leviticus 23:6) Firstfruits (Leviticus 23:10)

2 Iyyar (Ziv)

April–May

1 Kings 6:1, 37

Second Passover (Numbers 9:10–11)

3 Sivan

May–June

Esther 8:9

Pentecost (Weeks or Harvest) (Leviticus 23:16)

4 Tammuz

June–July

5 Ab

July–August

6 Elul

August–September

Nehemiah 6:15

7 Tishri (Ethanim)

September–October

1 Kings 8:2

Trumpets (New Year’s Day, Rosh Hashanah) (Leviticus 23:24; Numbers 29:1) Day of Atonement (Leviticus 23:27) Tabernacles (Shelters, Booths) (Leviticus 23:34)

8 Marcheshvan (Bul)

October–November

1 Kings 6:38

9 Chislev (also spelled Kislev)

November–December

Nehemiah 1:1

Dedication (Hanukkah) (John 10:22)

10 Tebeth

December–January

Esther 2:16

11 Shebat

January–February

Zechariah 1:7

12 Adar

February–March

Esther 3:7

Purim (Esther 9:24–32)

There is no known period in which the ancient Hebrews recorded dates by giving a month and day. Instead, they dated events by referring to an important event, such as the year when the current king began to rule.

In New Testament times, the Jews continued to use the same basic method found in the Old Testament. They connected events with dates in their religious calendar or with important events in the Roman world. New Testament writers used the same method (Luke 1:5; John 12:1; Acts 18:12).

Over time, the calendar reforms introduced by Julius Caesar became widely used. People then began to move from the older dating system to a more standard system.

In addition to keeping the Sabbath, Jews observe seven yearly festivals.

Passover takes place on the 14th day of Nisan. It remembers Israel’s deliverance from Egypt in the exodus. The first day of Nisan determines the date of Passover. Passover lasts seven days and includes the Feast of Unleavened Bread. This feast remembers how quickly the Israelites had to prepare to leave Egypt (Exodus 12:15). The festival of the firstfruits of the barley harvest follows immediately afterward (Leviticus 23:10).

Pentecost, the Feast of Weeks, is celebrated 50 days after Passover. It is a joyful festival connected with the firstfruits of the wheat harvest (Exodus 34:22; Leviticus 23:15–17).

New Year’s Day comes next and marks the beginning of Tishri. According to the rabbis, the first day of Tishri was the day when the Lord created the world. This day is called Rosh Hashanah, which means “head of the year.”

Yom Kippur, the Day of Atonement, is observed on the tenth day of Tishri. Atonement refers to how God deals with sin and restores people to a right relationship with him. Yom Kippur is the most serious day in Israel’s religious calendar. It is known as “the Sabbath of Sabbaths.” The Bible gives detailed instructions for observing this day (Leviticus 16).

Succoth, the Feast of Tabernacles, takes place from the 15th through the 22nd day of Tishri. It is mainly a harvest festival. It celebrates the crops gathered in September and October. The apostle John referred to it simply as “the feast” (John 7:37). The Feast of Tabernacles is also called the Feast of Booths or Shelters. It remembers how God cared for his people during Israel’s 40 years in the wilderness (Leviticus 23:39–43).

Hanukkah, the Feast of Dedication, began later in Jewish history. It remembers Judas Maccabeus’s decisive victory over Antiochus Epiphanes and the Syrians around 164 BC. Malachi, the last Old Testament prophet, lived long before this event. For this reason, tradition alone guides how the festival is celebrated. Hanukkah begins on the 25th day of Chislev and continues for seven more days. It is marked by joyful celebrations.

Purim is the final sacred festival of the year. It takes place on the 14th and 15th days of Adar. The festival began in ancient Persia. It remembers how Mordecai and Esther helped save the Jews by stopping Haman’s plan to destroy them (Esther 9).

Ancient sundials and modern clocks measure the passing of minutes and hours. In the same way, a calendar measures the passing of days, weeks, months, years, and even centuries.

Farming, business, and government all need a clear and consistent way to measure longer periods of time. Such a system is also important for historians. It also helps religious communities celebrate special days at the same time.

The modern Gregorian calendar developed through a combination of astronomy, history, and religious tradition. For Christians, the calendar also has religious meaning because the Bible contrasts God’s eternal nature with the shortness of human life (Psalm 90).

The psalmist asked God to “teach us to number our days, that we may present a heart of wisdom” (Psalm 90:12).

See also Astrology; Astronomy; Day; Feasts and Festivals of Israel; Jubilee Year; Moon; Night; Sun.