Fruit of the Spirit

Reconciling Dates

Finding a common frame of reference

This calculator page is provided as a service to students of judeo-christian history

Calculator functions require that Javascript be enabled in your browser, if you are sensible, you will verify that my scripts are not malicious, and enable scripts.

There are seven common ways of stating dates that are used for ancient times.

  1. Today's civil calendar bce/ce (formerly BC/AD) system, developed by Dionysius Exiguus about 525 after Jesus, by his reckoning, and popularised by Bede 200 years later.
  2. The Hebrew Year of the World (AM for latin Anno Mundi), counting from the traditional date of leaving Eden (sometimes called the Year of Adam in ancient texts).
  3. The years since the birth of Abraham, used in some ancient texts (AA).
  4. The Greek Olympiad system, counting by four-year Olympiads and year within the four.
  5. The year from the founding of Rome as a village (A.U.C.).
  6. The year from the establishment of the Greek Empire.
  7. By local reference, such as "the third year of Cyrus", the most commonly used in the source documents, and least informative.

Many ancient writers tried to establish the dates of events by cross referencing several local references, such as "the days of Uzziah in Judah and Jeroboam in Israel". The Greeks created one answer to the problem of each town having their own calendar and date of the new year with the Olympiad system, which, with variances in dates of the game, and local new-years, allows confidence in dating to within 18 months. The historian Eusebius ties dates in several systems together with entries cross-dated, viz "in the 18th Year of Xerxes in Persia, the first year of the 78th Olympiad, and the 1549th of Abraham" (Xerxes 18 = Ol 78.1 and 1549 AA). The Astrologer/astronomer Ptolemy of Alexandria compiled a cross reference of rulers and astronomical events, commonly called the Canon, which is one of the main sources of dates for this table of epochs.

Of our sources, one with a strong reputation for honest scholarship is Livius, which we can strongly recomend for further reading on many of the events in these timelines.

This site uses AM, which avoids dealing with any dates "Before Zero" within the span of recorded history, and makes math simple.

Dates and events are Israel-centric - The empires that sought to eliminate the Jews and their bothersome strict monotheism are dead history, Israel and the Hebrew language survive.

List of significant dates: Dates suitable as epoch bases have preload buttons

Concordant date calculator

To use the calculator, you can type an AM value into the Year of the World box and calculate everything else from there, or, you can use one of the three entry systems. System one, click a date button in the event list to load the epoch box and the Year of the World box, and calculate. System two, enter an Olympiad number and year, then click the calc button to load the Year of the World box, and calculate. System three, like the second, except enter BCE or CE or AD values in their boxes. The epoch calculation section allows extended calculation use; you can derive the epoch base from a starting pair such as having the AM value for the 15th year of Ahab.

The Jewish Jubilee cycle is included as a result, but not as a method of input. The Jubilee system is "weeks of years", with the land being given a "Sabath year" to recover after each six years of cultivation, and special significance given to the seventh Sabath year, the year of Jubilee. Some sources try to make the Jubilee year an extra, fiftieth, year, but the calculations are exact, requiring the anouncement of Jubilee on a specific date in the seventh Sabath year. Tradition places the first year of the first cycle as the date that Joshua led the people into Canaan to begin the occupation of the promised land. The positive identification of two Jubilee years in the times of Josiah and of Ezekiel lock down the year of the cycle, but how many cycles were completed in each case could be off. Jubilee data is not used for entry because it was not used to describe the dates of other events.

Calculate the approximate equivalent year

Since the varied calendars start their new year at varied points in the solar year, Results are plus or minus one (at least)

Calculate the Year of the World from the Olympiad

Olympiad number: Year within:

Calculate the Year of the World from CE

Year Number: BCE or CE:

Calculate the Year of the World from an arbitrary epoch

or, calculate the epoch from known reference points.

Year of the World at start of Epoch:

Year of the Epoch:

Calculate everything from the Year of the World

The Year of the World: (also used as third input for arbitrary epoch)

A companion to our series of timeline studies:

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