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How Did We Get Our Modern Calendar?

Written by Dianna Wiebe on .
INSIDE: Discover how biblical and modern calendars compare, and shape our understanding of time.

Have you ever wondered how we got our modern calendar? Have you read the Bible and noticed the months are different from the calendar hanging on your wall? Today, let’s explore how time was measured in the Bible compared to how time is measured today. Join me as we walk back in time to discover how our modern calendar came to be.

How Did the Ancient Calendars Measure Time?

Ancient civilizations measured time with a variety of calendars. While each was unique, in that they measured years differently. Ancient calendars followed one of three approaches: solar, lunar, or lunisolar.

  • The solar calendars are set based on the revolution of the earth around the sun. The Egyptians, for example, used a solar calendar with 365-day in each year.
  • Lunar Calendars: These track time by the phases of the moon. The Sumerians used a lunar calendar with 12 months per year, each lasting 29 to 30 days.
  • Lunisolar Calendars: These incorporate both the moon phases and the solar year. The biblical or Hebrew calendar is an example of a lunisolar calendar, where years are based on the solar year, but months follow the moon’s phases.
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 How Did We Get Our Modern Calendar?

Our modern calendar began with the Julian calendar, introduced by the Roman Empire in 46 BC under Julius Caesar. This calendar unified the empire and aligned with the solar year. Named after Caesar, the Julian calendar is still used by Eastern Orthodox churches to set holidays. Centuries later, it was replaced by the Gregorian calendar.

The Gregorian calendar, sometimes called the Christian Calendar, was introduced in 1582 by Pope Gregory XIII. Revisions included adding a leap year every four years and adjusting how Easter is determined. Today, the Gregorian calendar is used worldwide.

How are Days  and Weeks Measured on Different Calendars Today?

Depending on the calendar, days either begin at sunset or midnight. Similarly, weeks start on Sunday or Monday.

Gregorian Calendar

  • Days: Measured from midnight to midnight.
  • Weeks: Seven days long, starting with Sunday. The names of the days originate from Mesopotamian celestial bodies and Hellenistic astrology:
    • Sunday – Sun
    • Monday – Moon
    • Tuesday – Mars
    • Wednesday – Mercury
    • Thursday – Jupiter
    • Friday – Venus
    • Saturday – Saturn

Hebrew Calendar

  • Days: Measured from sunset to sunset.
  • Weeks: Seven days long, with names based on their relationship to the Sabbath:
    • Sunday – First day after Sabbath
    • Monday – Second day after Sabbath
    • Tuesday – Third day after Sabbath
    • Wednesday – Fourth day after Sabbath
    • Thursday – Fifth day after Sabbath
    • Friday – Sixth day after Sabbath
    • Saturday – Sabbath

How were the Months of the Year Named?

On the Gregorian calendar, months are named for Roman gods, officials, holidays, or Latin numbers. The calendar consists of 12 months, each lasting 28 to 31 days:

  • January: Roman god Janus
  • February: Roman holiday Ferua
  • March: Roman god Mars
  • April: Roman goddess Aphrodite
  • May: Roman goddess Maia
  • June: Roman god Juno
  • July: Julius Caesar
  • August: Augustus Caesar
  • September: Latin for seventh month
  • October: Latin for eighth month
  • November: Latin for ninth month
  • December: Latin for tenth month

How are Year Measured on the Modern Calendar?

Years on the Gregorian calendar are calculated in relation to the birth of Jesus. The year begins on January 1 and ends on December 31. Designations include:

  • BC: Before Christ, or BCE: Before Common Era
  • AD: Latin for “in the year of our Lord,” or CE: Common Era

This is a brief overview of how our modern calendar developed and how the days and months were named. Reflecting on how different calendars shape our understanding of time can deepen our appreciation of history and culture. If you’d like to explore further, take a look at our Biblical Events Calendar today!

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