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4. Appendices, continued






Appendix B: Dates





How to Record Dates



Specific Date Fields
General rules are discussed in this appendix. For rules specific to the particular Date you are recording, see the rules in this manual for the specific pertinent field: Dates for names/terms, dates for hierarchical relationships, dates for associative relationships. Note that rules for assigning dates are subject to variation from field to field.



General Rules for Recording Date
If you record a Display Date, it is required to record Start and End Dates. In all cases, if you fill in any one of the three fields, all three fields must be filled in.


Display, Start and End Dates
In the Display Date, record a year, a span of years, or a phrase that describes the specific or approximate date. In Start and End Dates, record years that delimit the span stated or implied in the Display Date. (Start and End Date will be hidden from end-users.)

    • Example
    • Display Date: ca. 1750
    • Start: 1745 End: 1755

  • Use the proleptic Gregorian calendar (the calendar produced by extending the Gregorian calendar to dates preceding its official introduction).

  • End users do not see Start and End Dates, thus you may estimate in these fields. Do not estimate Display Dates except when you have warrant in authoritative sources.



Capitalization and abbreviation
Do not capitalize words other than proper nouns or Period names. Avoid abbreviations, except with ca. (for circa), the numbers in century or dynasty designations (e.g., 17th century), and BCE and CE.

    • Examples
    • Display Date: ca. 1730-ca. 1750
    • Start: 1725 End: 1755

    • Display Date: 17th century
    • Start: 1600 End: 1699

    • Display Date: New Kingdom, 18th dynasty (1404-1365 BCE)
    • Start: -1404 End: -1365

  • Include all digits for both years in a span; for example, with four-digit years, do not abbreviate the second year (e.g., record 1780-1795, NOT 1780-95).





Use Arabic numbers. Express words and phrases in English, except in rare cases where no English-language equivalent exists or where the foreign term is most commonly used (e.g., with the name of a period). Use diacritical codes as required.





Format [1]
In the Display Date, use natural word order. For Start and End Dates, record appropriate numbers. Use negative numbers for years BCE (use a hyphen for the negative number). Do not use commas or other punctuation.

    • Examples
    • Display Date: relevant between 1950 and 1952
    • Start: 1950 End: 1952

    • Display Date: from the 2nd century BCE
    • Start: -300 End: 9999

** Syntax: Display dates
If a specific date is known, record the year. If a span of dates is applicable, record the year beginning of the span, dash, and the year ending the span.

    • Examples
    • Display Date: 1944
    • Start: 1944 End: 1944

    • Display Date: 1821-1826
    • Start: 1821 End: 1826

  • To express uncertainty or otherwise clarify the dates, place editorial commentary before the years (e.g., ca., founded, etc.) when possible. Use natural word order.

    • Examples
    • Display Date: ca. 1610
    • Start: 1605 End: 1615

    • Display Date: used 1911 or 1912
    • Start: 1911 End: 1912

    • Display Date: probably late 12th century
    • Start: 1150 End: 1220

** Syntax: Start and End Dates

  • Years: Record years in the Start and End Dates fields without commas or other punctuation, except for the dash/hyphen, which is used to express negative numbers for dates BCE. Use four digits for most years. Dates BCE may require more than four digits (e.g., -10000).

    • Examples
      [for a four-digit year CE]
    • Display Date: 1997
      Start: 1997 End: 1997

      [for a date BCE]
    • Display Date: 12-9 BCE
      Start: -12 End: -9

  • Month and day: Generally, the year is sufficiently specific. If the precise day is required, record the day, month, and year in the Display Date and index with only the year in the Start and End Dates. For the display date, the preferred syntax is day, month, year with no punctuation (e.g., 25 May 2000). The alternative syntax - month, day, comma, year - is found in many legacy records. Do not bother editing records that already contain this syntax, except in order to make the record consistent when you are editing the record.

    • Example
    • Display Date: 1 January through 25 May 2000
      Start: 2000 End: 2000





Dates BCE and CE
In the Display Date, use BCE (Before Common Era) to indicate dates before the year 1 in the proleptic Gregorian calendar.

    • Examples
    • Display Date: 463 BCE
      Start: -463 End: -463

    • Display Date: 221-206 BCE
      Start: -221 End: 206

  • For dates after the year 1, do not include the designation CE (Current Era), except where confusion may occur because 1) the span of dates begins BCE and ends CE (e.g., 75 BCE-10 CE) or 2) the date is within the first few centuries of the Current Era. Do not use BC (Before Christ) or AD (Anno Domini). Indicate dates BCE with negative numbers in Start and End Dates.

    • Examples
    • Display Date: 15 BCE-20 CE
      Start: -15 End: 20

    • Display Date: 312-315 CE
      Start: 312 End: 315

** Dates "years ago" or "before present"
For very ancient dates, BCE is generally not appropriate. Use the phrases years ago or before present if your source indicates age relative to the present rather than a date. Do not abbreviate designations (e.g., do not use y.a. or B.P.).

    • Example
    • Display Date: inhabited about 75,000 years ago
      Start: -76000 End: -70000

  • For Start and End Dates, translate the dates into the proleptic Gregorian calendar. Use an appropriate calibration table in the rare event that such a thing is readily available. [2]





Gregorian and other calendars
In general, record dates in the Display Date according to the proleptic Gregorian calendar.

  • If your source provides a date in another calendar (e.g., Julian, Napoleonic, or Islamic calendars), record it in the Display Date, clearly designating the alternate calendar. Also include the year in the proleptic Gregorian calendar to avoid confusion. Index the dates in the Start and End Dates using the proleptic Gregorian calendar.

    • Examples
    • Display Date: 946 anno Hegirae (1540 CE)
      Start: 1540 End: 1540

    • Display Date: année II de la Rèpublique (1794 CE)
      Start: 1794 End: 1794





If you are using a single year, explain what the year means in the Display Date. In Start and End Dates, record the estimated span of time referred to.

    • Examples
    • Display Date: use began in 689
      Start: 689 End: 720

    • Display Date: ended in 1643
      Start: 1550 End: 1643

  • When appropriate, express dates as a span of years, if known. Explain the significance of the span in the Display Date.

    • Example
    • Display Date: existed 1378-1485
      Start: 1378 End: 1485





Uncertain and approximate dates
If the specific year or years is not known, record dates with the greatest accuracy known. In the guidelines below, the conventions are arranged from greatest level of accuracy to the least; use the greatest possible level of accuracy, based on the information at hand.

** Probably
If there is doubt among authoritative sources, indicate this in the Display Date by using the word probably, possibly, or another appropriate word. Index such dates with Start and End Dates representing an appropriate span. Do not use probably if you simply lack information to make a decision; this refers only to uncertainty expressed in authoritative sources.

    • Example
    • Display Date: probably in existence in 1937
      Start: 1936 End: 1938

** Or
If the date is known to be one particular year or another, indicate this in the Display Date by using the word or. Do not use or if you simply lack information to make a decision; this refers only to uncertainty expressed in authoritative sources.

    • Example
    • Display Date: 1568 or 1569
      Start: 1568 End: 1569

** Circa
If the precise date is unknown, preface the year with ca. (for circa) or about. Estimate Start and End Dates based on available information. If appropriate for the situation at hand, use a 10-year span for Start and End Dates for circa (e.g., ca. 1860 could be indexed Start: 1855, End: 1865); for ancient dates, use a much larger span (e.g., ca. 1200 BCE could be indexed Start: -1250, End: -1150). Do not use ca. if you simply lack information to make a decision; this refers only to uncertainty expressed in authoritative sources.

    • Examples
    • Display Date: ca. 1935
      Start: 1930 End: 1940

    • Display Date: ca. 500 BCE
      Start: -0550 End: -0450

  • If ca. is used with a span of dates, repeat it as necessary to indicate whether it applies to the beginning year, the ending year, or both years of the span. Estimate Start and End Dates as appropriate.

    • Examples
    • Display Date: ca. 1505-ca.1510
      Start: 1500 End: 1515

    • Display Date: established ca. 1750-1756
      Start: 1745 End: 9999

    • Display Date: known from 1834-ca. 1850
      Start: 1834 End: 9999

  • Preface centuries or other broad dates with ca. as needed. Estimate Start and End Dates appropriately, based on available information.

    • Example
    • Display Date: ca. 19th century
      Start: 1750 End: 9999

  • About: For very ancient dates, use the word about rather than ca.

    • Example
    • Display Date: began about 18,000 years ago
      Start: -19000 End: -10000

** Before and after
If appropriate, express dates relative to a terminus ante quem or a terminus post quem (meaning date before which and date after which). In the Display Date, use the words before or after. Estimate Start and End Dates based on available information.

    • Examples
    • Display Date: known before 1758
      Start: 1750 End: 9999

    • Display Date: known after 547
      Start: 547 End: 9999

** Spans indicating uncertainty
If appropriate, record the span of years appropriate for the field. Distinguish between 1) the span indicating that a precise date is unknown, but the date applies to some unknown point during the span, and 2) the span that is known, for example, during which a style was prominent. Clearly describe the meaning of the date in the Display Date rather than using subtle differences in punctuation, such as a dash/hyphen or forward slash, to convey differences in meaning.

    • Examples
    • Display Date: between 1559 and 1562
      Start: 1559 End: 1562

      [date implies a broad span]
    • Display Date: from 3rd or 2nd century BCE
      Start: -299 End: 9999

  • Dash vs. forward slash: A dash or forward slash may be used in the following ways, provided it will be clear from the context what is meant. Use the dash to indicate a span during which something occurred, as when a ruler ruled (e.g., ca. 1435 - ca. 1560 means that rule occurred from ca. 1435 to ca. 1560). Use the forward slash when a specific date is not known, to indicate a span that contains some year or years when the event occurred (e.g., 1735/1745 means the date is uncertain but the event occurred sometime between 1735 and 1745).

** Decades and centuries
Where appropriate, indicate the date to the nearest decade or century, when appropriate. Do not use an apostrophe with decades (e.g., 1890s, NOT 1890's).

    • Examples
    • Display Date: 1890s
      Start: 1890 End: 1899

    • Display Date: 1720s or 1730s
      Start: 1720 End: 1739

    • Display Date: 16th century
      Start: 1500 End: 1599

    • Display Date: 2nd century BCE
      Start: -199 End: -100

  • Qualify decades or centuries with early, mid-, and late, as warranted. Assign appropriate Start and End Dates, dividing the century into thirds (e.g., late 18th century may be indexed as the last third of the century, Start: 1770, End: 1799).

    • Examples
    • Display Date: late 18th century
      Start: 1770 End: 1799

    • Display Date: late 12th or early 11th century BCE
      Start: -1130 End: -1070

** Dates by Period or era
When a more exact date is not known, express dates according to a named period, dynasty, or ruler's reign, if appropriate. The periods may be divided into early, middle, or late. Start and End Dates for retrieval should be based on dates applicable for that period. In some cases, the Period named in Date may be the same as the Period recorded in Style.

    • Examples

    • Display Date: Late Archaic Period
      Start: -2000 End: -1000

    • Display Date: Medieval
      Start: 1100 End: 1499

    • Display Date: reign of Shah Jahan (1628-1657)
      Start: 1628 End: 1657

** No Date
Do not use n.d. (for "no date"). Do not leave the date fields blank. If a date is uncertain, determine a possible date range based on available information.










How to Use the Date Authority





Using the Date Authority
The Date Authority is intended only as a reference tool; it is an incomplete and extensible list and may not apply to your specific situation. You must fill in all three fields (display, start and end), so estimate a value if the field is blank in the authority below.





Display Date
In the display date, write precisely what you know from your research (e.g., "possibly an Upper Paleolithic tool").

  • DO NOT give precise dates when only approximate dates or broad periods are known. Be careful - terms such as "period," "age" and "era" have specialized meanings in these contexts, so be sure to use them as they are used in your authoritative source; also, you must use initial capitalization correctly.

  • Any text in parentheses below should NOT be included in your display date; it is for your information only.





Time scales
There can be overlap between different time scales (e.g., between Geologic time scale and cultural time scale, or between cultural periods such as Bronze Age in different parts of the world). For Start and End Dates, estimate broad range for searching; if your source indicates a range of dates different from those indicated below, use the dates in the source rather than those below.

  • The abbreviations BCE, CE, and "ca." are permissible in display dates.

  • For "years before present," in display dates, type out the entire phrase (valid abbreviations in display dates are the following. For Start and End Dates, calculate negative values as years Before Common Era (i.e., in the proleptic Gregorian calendar).





Estimating Start and End Dates
For Start and End Dates, use your head. Don't just copy dates from the authority below, but instead consider available information relative to the situation at hand. For example, if you are determining searching dates for a type of tool and your source says remains of Neanderthals have been found with the tool, DO NOT blindly copy -800000 and -10000 as Start and End Dates; instead, use these years to estimate a terminus a quo for the earliest possible date (and look to other information to see what End Date is appropriate for this particular case; if it is still inhabited, the End Date is 9999).






Date Authority of Approximate Dates for Named Periods, Etc.


Name of the Period

Date range of the Period



Years ago


Precambrian Era

-600000000 to


Paleozoic Era

-600000000 to -230000000


Cambrian Period

-600000000 to -500000000


Ordovician Period

-500000000 to -425000000


Silurian Period

-425000000 to -405000000


Devonian Period

-405000000 to -345000000


Carboniferous Period

-345000000 to -280000000


Mississippian (Lower Carboniferous)

-345000000 to -310000000


Pennsylvanian (Upper Carboniferous)

-310000000 to -280000000


Permian Period

-280000000 to -230000000


Mesozoic Era

-230000000 to -63000000


Triassic Period

-230000000 to -180000000


Jurassic Period

-180000000 to -135000000


Cretaceous Period

-135000000 to -63000000


Cenozoic Era

-63000000 to present


Tertiary Period

-63000000 to -500000


Paleocene Epoch

-63000000 to -58000000


Eocene Epoch

-58000000 to -36000000


Oligocene Epoch

-36000000 to -25000000


Miocene Epoch

-25000000 to -13000000


first hominids

-8000000 to -5000000


Pliocene Epoch

-13000000 to -500000


Australopithecines emerge

-5000000 to -3000000


Homo habilis emerges

-3500000 to -2500000


Quaternary Period

-2000000 to present


Pleistocene Epoch (Glacial)

-2000000 to -11000


Robust Australopithecines emerge

-2000000 to -1800000


Homo erectus in Java

-1000000 to -750000


Homo erectus in China

-1000000 to -200000


archaic Homo sapiens in Africa

-1000000 to -200000


archaic Homo sapiens in Europe

-1000000 to -200000


modern Homo sapiens emerge

-300000 to -200000


Homo sapiens Neanderthal in Europe

-300000 to -10000



BCE and-CE


Holocene Epoch (Recent)

-11000 to present


Stone Age




-35000 to -10000


Lower Paleolithic Period



Middle Paleolithic Period



Upper Paleolithic Period



Migrations fr. Asia to Americas

-30000 to


Epipaleolithic Period



Mesolithic Period

-10000 to -8000


Neolithic Period

-8000 to -4000


Early Neolithic



Middle Neolithic



Late Neolithic



Sumerians settle in Mesopotamia

-5000 to


Narmer-Menes unites Upper/Lower Egypt



Narmer-Menes unites Upper/Lower Egypt

-3000 to -2340


Mongoloid and Melanotic sites in Oceania



Niger-Kordofanian culture, Africa

-3000 to 1000


Chalcolithic (Copper Age)



Early Chalcolithic



Narmer-Menes unites Upper/Lower Egypt



Middle Chalcolithic



Late Chalcolithic






Final Neolithic



Bronze Age



Early Bronze Age



Protodynastic period, Sumer

-3000 to -2340

Langer, World History

Middle Bronze Age



First Intermediate Period, Egypt

-2155 to -2040


Middle Kingdom, Egypt

-2040 to -1785


Second Intermediate Period-Hyksos, Egypt

-1786 to -1554


Mesopotamia under Babylonians, Hammurabi

-1792 to -1750

Langer, World History

Minoans flourish

-1600 to -1400

Langer, World History

Late Bronze Age



Cycladic colonies develop



Egyptian Empire

-1554 to -1080


Amonhotep I






Amonhotep III






Seti I



Ramses II



Urnfield culture, ctrl Europe

-1300 to -500


Iron Age in Europe



Early Iron Age



Assyrian Empire

-1000 to -612


Neo-Babylonian Period, Nebuchadnezzar II



Archaic Greek




-800 to 100


Dorians invade Greece



Ionians resettle in Asia Minor



Mycenae destroyed



Greek colonies in Italy



Middle Iron Age



Persian Empire

-559 to -323


Cyrus the Great

-559 to -529


Late Iron Age



Persian Wars

-499 to -478


Delian League

-479 to -461

NYPL, Chronologies

Periclean Age

-460 to -429


Peloponnesian War

-431 to -404


Philip of Macedon

-359 to -336

NYPL, Chronologies

Alexander the Great, King of Macedon

-336 to -323



-650 to -500

Times (1989), 86

Roman Republican


Times (1989), 86

Gauls sack Rome



First Punic War

-264 to -241


Sulla becomes dictator

-82 to -79


First triumvirate, Pompey, Caesar, Crassus





















Caesar assumes power

-49 to -44


Second triumvirate, Octavius



Roman Imperial


Hartt, History of Ptg.

Octavius becomes Augustus Caesar

-27 to 14


Jesus Christ

-3 to 30



14 to 68











Paul, Christianity in Asia Minor, etc.




69 to 96












98 to 117



117 to 138



138 to 180


Antoninus Pius



Marcus Aurelius






Ptolomy, astronomer




50 to 120


Septimus Severus

193 to 211



211 to 217


Scythians flourish



Celts flourish



Christian persecution by Rome



Early Christian Period

50 to 300



284 to 305





Shapur I, Sassanian king of Persia

242 to 272


Vakatakas, S Indian dynasty

250 to 390


Gupta empire, India






Constantine the Great

324 to 337


Huns displace Vandals in central Europe



First Council of Nicea



Theodosius divides Empire



Western Roman Empire

395 to 476


Honorius makes Ravenna capital of West



Alaric I, Visogoths sack Rome



Vandals invade North Africa



Attila and Huns destroys Milan



Odoacer takes Ravenna



Theodoric founds Ostrogothic kingdom, Italy

488 to 526


Council of Ephesus



St. Patrick, Christians in Ireland



Justinian is Emperor of Byzantium

527 to 565


Anglo/Saxons, Germanic tribes in England

400 to 1100


Uzbeks arrive in Tashkent



Lombards establish kingdom in Italy



Muhammad, prophet of Islam

560 to 632


Muslims conquer Byzantine Near East, NAfrica

637 to 640


Second Council of Nicea




500 to 1500


Omayyad caliphate, Damascus

661 to 750


Abbasid caliphate, Baghdad

750 to 1256


Uighurs, nomadic Turkic, ctrl Asia

700 to 900


Carolingian Period



Charlemagne crowned Emperor, Rome



Charles the Bald

840 to 877


Carolingian kingdom divided, Treaty of Verdun



Macedonian Dynasty

829 to 976


Vikings raid England



Charles the Simple cedes Normandy to Vikings






Otto I, German crowned Holy Roman Emperor



Zirids, Muslim Berber dynasty

972 to 1152


Vladimir I, Duke of Kiev

980 to 1015


Capetian Dynasty



Hugh Capet, French king

987 to 996


Schism between Eastern & Western Church



Russia converts to Orthodox Church







900 to 1200


Italian city-states established



William the Conqueror, Norman duke

1035 to 1087


Battle of Hastings



First Crusade

1095 to 1099


Latin kingdom of Jerusalem founded



Roger II, king of Sicily

1130 to 1154


Louis IV the Fat, of France

1108 to 1137


Second Crusade

1147 to 1187


St. Bernard, abbot of Clairvaux

1115 to 1153


Order of Knights Templars, Jerusalem



Saladin captures Jerusalem




1050 to 1450


Zagwe, Ethiopian Semitic dynasty

1100 to 1300


Third Crusade

1189 to 1192


Angevin Dynasty (Plantagenets), England

1154 to 1399


Henry II

1154 to 1189


Richard II

1377 to 1399


Fourth Crusade

1202 to 1204


Sack Constantinople



Latin Empire of the East

1204 to 1261


Moors in Europe



St. Louis IX, French king

1226 to 1270


Magna Carta signed in England



Sixth Crusade, Frederick II

1228 to 1229


Seventh Crusade, Louis IX

1248 to 1254


Eighth Crusade



Marco Polo goes to China and India

1265 to 1293


Papacy in Avignon

1309 to 1378


Hundred Years War, France and England

1337 to 1453


Black Death epidemic in Europe

1347 to 1350



1400 to 1600


Sunni Ali, Emperor of Songha W Africa

1464 to 1492


Age of Exploration

1395 to 1750


Prince Henry the Navigator of Portugal

1394 to 1460


Christopher Columbus charts America



Magellan, circumnavigated globe

1475 to 1521


Bartholomew Diaz rounds Cape Good Hope



Balboa sights Pacific Ocean



Hapsburgs begin rule of Holy Roman Empire



Constantinople falls to Turks



Tudor period, England



Henry VII, king of England

1485 to 1509


Gregorian Calendar, Pope Gregory XIII



Pope Julius II

1503 to 1513


Pope Leo X

1513 to 1521


Mannerist style

1510 to 1600


Martin Luther

1483 to 1546


Lutheran/Catholic Wars in Germany end



Jesuit religious order founded






Baroque style

1600 to 1700


Pope Sixtus V

1585 to 1590


Edict of Nantes, religious tolerance in France 1598



Pope Paul V

1605 to 1621


Pope Innocent X

1644 to 1655


Pope Alexander VII

1655 to 1667


Great Fire of London






Rococo style

1650 to 1775


Louis XV, France

1715 to 1774


Ashanti culture, Ivory Coast, etc

1700 to 1900


Sikhs, Indian religious community



Frederick II the Great of Prussia 1748



Seven Years War

1756 to 1763


American Revolution

1775 to 1783


Catherine the Great of Russia

1762 to 1796


Excavations at Pompeii & Herculaneum, etc.



French Revolution

1789 to 1797



1799 to 1815


Neoclassicism (style)






Realism (style)



Impressionism (style)



Post-Impressionism (style)



Sioux (Dakota) culture



Industrial Revolution



Zulu empire, Africa

1810 to 1879


Crimean War

1853 to 1856


Peace of Zurich, Napoleon III & Franz Joseph



Unification of Italy

1860 to 1870


American Civil War

1861 to 1865


Spanish-American War



Revolution in China, republic founded



World War I

1914 to 1918


Bolshevik Revolution in Russia



Spanish Civil War

1936 to 1939


World War II

1939 to 1945


United Nations Charter



Israel is independent



Korean War

1950 to 1953


Common Market established in Europe



Six-Day War, Middle East



Vietnam War



Dissolution of the Soviet Union






[1]Dates are compliant with ISO standards; however, the standard advises that dates comprising fewer than four digits should be padded with leading zeroes. VCS/Oracle will not allow leading zeroes. The zeroes may be added by implementers after the data is published. The ISO standard is the following: ISO 8601:2004 Representation of dates and times. International Organization for Standardization. Data Elements and Interchange Formats. Information Interchange. Representation of Dates and Times. Geneva, Switzerland: International Organization for Standardization, 2004.


2Note that years in ages estimated by radiocarbon dating, potassium/argon dating, and other such relative dating methods do not necessarily correspond to years recorded in a calendar; therefore, calibration tables are designed for the particular circumstances surrounding the specific relative dating process. Calibration tables are often unavailable; however, dates should still be estimated because the fields may not be left blank and slight inaccuracies in Earliest and Latest Dates will not affect overall retrieval.


Last updated 28 March 2006
Document is subject to frequent revisions


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