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Before Present

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"YBP" and "ybp" redirect here. For other uses, see YBP (disambiguation).

Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale, with 1950 being labelled as the "standard year". The abbreviation "BP" has been interpreted retrospectively as "Before Physics",[1][2] which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must account for.[3][4]

In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP stands for the explicit "radio carbon years before/prior present".

Usage

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The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy.[5][6] This usage differs from the recommendation by van der Plicht & Hogg,[7] followed by the Quaternary Science Reviews,[8][9] both of which requested that publications should use the unit "a" (for "annum", Latin for "year") and reserve the term "BP" for radiocarbon estimations.

Some archaeologists use the lowercase letters bp, bc and ad as terminology for uncalibrated dates for these eras.[10]

The Centre for Ice and Climate at the University of Copenhagen instead uses the unambiguous "b2k", for "years before 2000 AD", often in combination with the Greenland Ice Core Chronology 2005 (GICC05) time scale.[11]

Some authors who use the YBP dating format also use YAP (years after present) to denote years after 1950.[12]

SI prefixes

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SI prefix multipliers may be used to express larger periods of time, e.g. ka BP (thousand years BP), Ma BP (million years BP) and many others.[13]

Radiocarbon dating

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Radiocarbon dating was first used in 1949.[14][15] Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid. According to scientist A. Currie Lloyd:

The problem was tackled by the international radiocarbon community in the late 1950s, in cooperation with the U.S. National Bureau of Standards. A large quantity of contemporary oxalic acid dihydrate was prepared as NBS Standard Reference Material (SRM) 4990B. Its 14C concentration was about 5% above what was believed to be the natural level, so the standard for radiocarbon dating was defined as 0.95 times the 14C concentration of this material, adjusted to a 13C reference value of −19 per mil (PDB). This value is defined as "modern carbon" referenced to AD 1950. Radiocarbon measurements are compared to this modern carbon value, and expressed as "fraction of modern" (fM). "Radiocarbon ages" are calculated from fM using the exponential decay relation and the "Libby half-life" 5568 a. The ages are expressed in years before present (BP) where "present" is defined as AD 1950.[16]

The year 1950 was chosen because it was the standard astronomical epoch at that time.[citation needed] It also marked[3] the publication of the first radiocarbon dates in December 1949,[17] and 1950 also antedates large-scale atmospheric testing of nuclear weapons, which altered the global ratio of carbon-14 to carbon-12.[18]

Radiocarbon calibration

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Main article: Radiocarbon dating § Calibration

Dates determined using radiocarbon dating come as two kinds: uncalibrated (also called Libby or raw) and calibrated (also called Cambridge) dates.[19] Uncalibrated radiocarbon dates should be clearly noted as such by "uncalibrated years BP", because they are not identical to calendar dates. This has to do with the fact that the level of atmospheric radiocarbon (carbon-14 or 14C) has not been strictly constant during the span of time that can be radiocarbon-dated. Uncalibrated radiocarbon ages can be converted to calendar dates by calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods, such as dendrochronology (dating based on tree growth-rings) and stratigraphy (dating based on sediment layers in mud or sedimentary rock). Such calibrated dates are expressed as cal BP, where "cal" indicates "calibrated years", or "calendar years", before 1950.

Many scholarly and scientific journals require that published calibrated results be accompanied by the name (standard codes are used) of the laboratory concerned, and other information such as confidence levels, because of differences between the methods used by different laboratories and changes in calibrating methods.

Conversion

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Conversion from Gregorian calendar years to Before Present years is by starting with the 1950-01-01 epoch of the Gregorian calendar and increasing the BP year count with each year into the past from that Gregorian date.

For example, 1000 BP corresponds to 950 AD, 1949 BP corresponds to 1 AD, 1950 BP corresponds to 1 BC, 2000 BP corresponds to 51 BC.

Example milestone years in the BP time scale
Gregorian year BP year Event
9701 BC 11650 BP End of the Pleistocene and beginning of the Holocene epoch[20]
4714 BC 6663 BP Epoch of the Julian day system: Julian day 0 starts at Greenwich noon on January 1, 4713 BC of the proleptic Julian calendar, which is November 24, 4714 BC in the proleptic Gregorian calendar[21]: 10 
2251 BC 4200 BP Beginning of the Meghalayan age, the current and latest of the three stages in the Holocene era.[22][23]
45 BC 1994 BP Introduction of the Julian calendar
1 BC 1950 BP Year zero in ISO 8601
AD 1 1949 BP Beginning of the Common Era and Anno Domini, from the estimate by Dionysius of the Incarnation of Jesus
1582 368 BP Introduction of the Gregorian calendar[21]: 47 
1950 – Epoch of the Before Present dating scheme[24]: 190 
2024 74 YAP Current year

Before Present Millennia List. (BP)

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1st Millennium BP: 1950 CE - 950 CE

2nd Millennium BP: 951 CE - 1950 BCE

3rd Millennium BP: 1951 BCE - 2950 BCE

4th Millennium BP: 2951 BCE - 3950 BCE

5th Millennium BP: 3951 BCE - 4950 BCE

6th Millennium BP: 4951 BCE - 5950 BCE

7th Millennium BP: 5951 BCE - 6950 BCE

8th Millennium BP: 6951 BCE - 7950 BCE

9th Millennium BP: 7951 BCE - 8950 BCE

10th Millennium BP: 8951 BCE - 9950 BCE

11th Millennium BP: 9951 BCE - 10,950 BCE

12th Millennium BP: 10,951 BCE - 11,950 BCE

13th Millennium BP: 11,951 BCE - 12,950 BCE

14th Millennium BP: 12,951 BCE - 13,950 BCE

15th Millennium BP: 13,951 BCE - 14,950 BCE

16th Millennium BP: 14,951 BCE - 15,950 BCE

17th Millennium BP: 15,951 BCE - 16,950 BCE

18th Millennium BP: 16,951 BCE - 17,950 BCE

19th Millennium BP: 17,951 BCE - 18,950 BCE

20th Millennium BP: 18,951 BCE - 19,950 BCE

21st Millennium BP: 19,951 BCE - 20,950 BCE

22nd Millennium BP: 20,951 BCE - 21,950 BCE

23rd Millennium BP: 21,951 BCE - 22,950 BCE

24th Millennium BP: 22,951 BCE - 23,950 BCE

25th Millennium BP: 23,951 BCE - 24,950 BCE

26th Millennium BP: 24,951 BCE - 25,950 BCE

27th Millennium BP: 25,951 BCE - 26,950 BCE

28th Millennium BP: 26,951 BCE - 27,950 BCE

29th Millennium BP: 27,951 BCE - 28,950 BCE

30th Millennium BP: 28,951 BCE - 29,950 BCE

31st Millennium BP: 29,951 BCE - 30,950 BCE

32nd Millennium BP: 30,951 BCE - 31,950 BCE

33rd Millennium BP: 31,951 BCE - 32,950 BCE

34th Millennium BP: 32,951 BCE - 33,950 BCE

35th Millennium BP: 33,951 BCE - 34,950 BCE

36th Millennium BP: 34,951 BCE - 35,950 BCE

37th Millennium BP: 35,951 BCE - 36,950 BCE

38th Millennium BP: 36,951 BCE - 37,950 BCE

39th Millennium BP: 37,951 BCE - 38,950 BCE

40th Millennium BP: 38,951 BCE - 39,950 BCE

41st Millennium BP: 39,951 BCE - 40,950 BCE

42nd Millennium BP: 40,951 BCE - 41,950 BCE

43rd Millennium BP: 41,951 BCE - 42,950 BCE

44th Millennium BP: 42,951 BCE - 43,950 BCE

45th Millennium BP: 43,951 BCE - 44,950 BCE

46th Millennium BP: 44,951 BCE - 45,950 BCE

47th Millennium BP: 45,951 BCE - 46,950 BCE

48th Millennium BP: 46,951 BCE - 47,950 BCE

49th Millennium BP: 47,951 BCE - 48,950 BCE

50th Millennium BP: 48,951 BCE - 49,950 BCE

51st Millennium BP: 49,951 BCE - 50,950 BCE


After Present Millennia List. (AP)

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1. 1st Millennium AP: 1950 CE to 2950 CE

2. 2nd Millennium AP: 2951 CE to 3950 CE

3. 3rd Millennium AP: 3951 CE to 4950 CE

4. 4th Millennium AP: 4951 CE to 5950 CE

5. 5th Millennium AP: 5951 CE to 6950 CE

6. 6th Millennium AP: 6951 CE to 7950 CE

7. 7th Millennium AP: 7951 CE to 8950 CE

8. 8th Millennium AP: 8951 CE to 9950 CE

9. 9th Millennium AP: 9951 CE to 10,950 CE

10. 10th Millennium AP: 10,951 CE to 11,950 CE

11. 11th Millennium AP: 11,951 CE to 12,950 CE

12. 12th Millennium AP: 12,951 CE to 13,950 CE

13. 13th Millennium AP: 13,951 CE to 14,950 CE

14. 14th Millennium AP: 14,951 CE to 15,950 CE

15. 15th Millennium AP: 15,951 CE to 16,950 CE

16. 16th Millennium AP: 16,951 CE to 17,950 CE

17. 17th Millennium AP: 17,951 CE to 18,950 CE

18. 18th Millennium AP: 18,951 CE to 19,950 CE

19. 19th Millennium AP: 19,951 CE to 20,950 CE

20. 20th Millennium AP: 20,951 CE to 21,950 CE

21. 21st Millennium AP: 21,951 CE to 22,950 CE

22. 22nd Millennium AP: 22,951 CE to 23,950 CE

23. 23rd Millennium AP: 23,951 CE to 24,950 CE

24. 24th Millennium AP: 24,951 CE to 25,950 CE

25. 25th Millennium AP: 25,951 CE to 26,950 CE

26. 26th Millennium AP: 26,951 CE to 27,950 CE

27. 27th Millennium AP: 27,951 CE to 28,950 CE

28. 28th Millennium AP: 28,951 CE to 29,950 CE

29. 29th Millennium AP: 29,951 CE to 30,950 CE

30. 30th Millennium AP: 30,951 CE to 31,950 CE

31. 31st Millennium AP: 31,951 CE to 32,950 CE

32. 32nd Millennium AP: 32,951 CE to 33,950 CE

33. 33rd Millennium AP: 33,951 CE to 34,950 CE

34. 34th Millennium AP: 34,951 CE to 35,950 CE

35. 35th Millennium AP: 35,951 CE to 36,950 CE

36. 36th Millennium AP: 36,951 CE to 37,950 CE

37. 37th Millennium AP: 37,951 CE to 38,950 CE

38. 38th Millennium AP: 38,951 CE to 39,950 CE

39. 39th Millennium AP: 39,951 CE to 40,950 CE

40. 40th Millennium AP: 40,951 CE to 41,950 CE

41. 41st Millennium AP: 41,951 CE to 42,950 CE

42. 42nd Millennium AP: 42,951 CE to 43,950 CE

43. 43rd Millennium AP: 43,951 CE to 44,950 CE

44. 44th Millennium AP: 44,951 CE to 45,950 CE

45. 45th Millennium AP: 45,951 CE to 46,950 CE

46. 46th Millennium AP: 46,951 CE to 47,950 CE

47. 47th Millennium AP: 47,951 CE to 48,950 CE

48. 48th Millennium AP: 48,951 CE to 49,950 CE

49. 49th Millennium AP: 49,951 CE to 50,950 CE

50. 50th Millennium AP: 50,951 CE to 51,950 CE

Before Present Century List. (BP)

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1st Century BP: 1950 CE - 1851 CE

2nd Century BP: 1850 CE - 1751 CE

3rd Century BP: 1750 CE - 1651 CE

4th Century BP: 1650 CE - 1551 CE

5th Century BP: 1550 CE - 1451 CE

6th Century BP: 1450 CE - 1351 CE

7th Century BP: 1350 CE - 1251 CE

8th Century BP: 1250 CE - 1151 CE

9th Century BP: 1150 CE - 1051 CE

10th Century BP: 1050 CE - 951 CE

11th Century BP: 950 CE - 851 CE

12th Century BP: 850 CE - 751 CE

13th Century BP: 750 CE - 651 CE

14th Century BP: 650 CE - 551 CE

15th Century BP: 550 CE - 451 CE

16th Century BP: 450 CE - 351 CE

17th Century BP: 350 CE - 251 CE

18th Century BP: 250 CE - 151 CE

19th Century BP: 150 CE - 51 CE

20th Century BP: 50 CE - 51 BCE

21st Century BP: 50 BCE - 151 BCE

22nd Century BP: 150 BCE - 251 BCE

23rd Century BP: 250 BCE - 351 BCE

24th Century BP: 350 BCE - 451 BCE

25th Century BP: 450 BCE - 551 BCE

26th Century BP: 550 BCE - 651 BCE

27th Century BP: 650 BCE - 751 BCE

28th Century BP: 750 BCE - 851 BCE

29th Century BP: 850 BCE - 951 BCE

30th Century BP: 950 BCE - 1051 BCE

31st Century BP: 1050 BCE - 1151 BCE

32nd Century BP: 1150 BCE - 1251 BCE

33rd Century BP: 1250 BCE - 1351 BCE

34th Century BP: 1350 BCE - 1451 BCE

35th Century BP: 1450 BCE - 1551 BCE

36th Century BP: 1550 BCE - 1651 BCE

37th Century BP: 1650 BCE - 1751 BCE

38th Century BP: 1750 BCE - 1851 BCE

39th Century BP: 1850 BCE - 1951 BCE

40th Century BP: 1950 BCE - 2051 BCE

41st Century BP: 2050 BCE - 2151 BCE

42nd Century BP: 2150 BCE - 2251 BCE

43rd Century BP: 2250 BCE - 2351 BCE

44th Century BP: 2350 BCE - 2451 BCE

45th Century BP: 2450 BCE - 2551 BCE

46th Century BP: 2550 BCE - 2651 BCE

47th Century BP: 2650 BCE - 2751 BCE

48th Century BP: 2750 BCE - 2851 BCE

49th Century BP: 2850 BCE - 2951 BCE

50th Century BP: 2950 BCE - 3051 BCE

51st Century BP: 3050 BCE - 3151 BCE


After Present Century List. (AP)

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1st Century AP: 1950 CE - 2050 CE

2nd Century AP: 2051 CE - 2150 CE

3rd Century AP: 2151 CE - 2250 CE

4th Century AP: 2251 CE - 2350 CE

5th Century AP: 2351 CE - 2450 CE

6th Century AP: 2451 CE - 2550 CE

7th Century AP: 2551 CE - 2650 CE

8th Century AP: 2651 CE - 2750 CE

9th Century AP: 2751 CE - 2850 CE

10th Century AP: 2851 CE - 2950 CE

11th Century AP: 2951 CE - 3050 CE

12th Century AP: 3051 CE - 3150 CE

13th Century AP: 3151 CE - 3250 CE

14th Century AP: 3251 CE - 3350 CE

15th Century AP: 3351 CE - 3450 CE

16th Century AP: 3451 CE - 3550 CE

17th Century AP: 3551 CE - 3650 CE

18th Century AP: 3651 CE - 3750 CE

19th Century AP: 3751 CE - 3850 CE

20th Century AP: 3851 CE - 3950 CE

21st Century AP: 3951 CE - 4050 CE

22nd Century AP: 4051 CE - 4150 CE

23rd Century AP: 4151 CE - 4250 CE

24th Century AP: 4251 CE - 4350 CE

25th Century AP: 4351 CE - 4450 CE

26th Century AP: 4451 CE - 4550 CE

27th Century AP: 4551 CE - 4650 CE

28th Century AP: 4651 CE - 4750 CE

29th Century AP: 4751 CE - 4850 CE

30th Century AP: 4851 CE - 4950 CE

31st Century AP: 4951 CE - 5050 CE

32nd Century AP: 5051 CE - 5150 CE

33rd Century AP: 5151 CE - 5250 CE

34th Century AP: 5251 CE - 5350 CE

35th Century AP: 5351 CE - 5450 CE

36th Century AP: 5451 CE - 5550 CE

37th Century AP: 5551 CE - 5650 CE

38th Century AP: 5651 CE - 5750 CE

39th Century AP: 5751 CE - 5850 CE

40th Century AP: 5851 CE - 5950 CE

41st Century AP: 5951 CE - 6050 CE

42nd Century AP: 6051 CE - 6150 CE

43rd Century AP: 6151 CE - 6250 CE

44th Century AP: 6251 CE - 6350 CE

45th Century AP: 6351 CE - 6450 CE

46th Century AP: 6451 CE - 6550 CE

47th Century AP: 6551 CE - 6650 CE

48th Century AP: 6651 CE - 6750 CE

49th Century AP: 6751 CE - 6850 CE

50th Century AP: 6851 CE - 6950 CE

51st Century AP: 6951 CE - 7050 CE

See also

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Citations

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  1. ^ Flint, Richard Foster; Deevey, Edward S (1962). "Volume 4 – 1962". Radiocarbon. 4 (1): i.
  2. ^ van der Plicht, Johannes (January 2004). "Radiocarbon, the Calibration Curve and Scythian Chronology". NATO Science Series: IV: Earth and Environmental Sciences (PDF). Vol. 42. Dordrecht: Springer Netherlands. pp. 45–61 (47). doi:10.1007/1-4020-2656-0_5. ISBN 978-1-4020-2655-3. Archived from the original (PDF) on 2011-07-24. Retrieved 8 August 2024.
  3. ^ a b Taylor RE (1985). "The beginnings of radiocarbon dating in American Antiquity: a historical perspective". American Antiquity. 50 (2): 309–325. doi:10.2307/280489. JSTOR 280489. S2CID 163900461.
  4. ^ Dincauze, Dena (2000). "Measuring time with isotopes and magnetism". Environmental Archaeology: Principles and Practice. Cambridge, England: Cambridge University Press. p. 110. ISBN 978-0-5213-1077-2.
  5. ^ "AGU Editorial Style Guide for Authors". American Geophysical Union. 21 September 2007. Archived from the original on 2008-07-14. Retrieved 2009-01-09.
  6. ^ North American Commission on Stratigraphic Nomenclature (November 2005). "North American Stratigraphic Code: Article 13 (c)". The American Association of Petroleum Geologists Bulletin. 89 (11): 1547–1591. doi:10.1306/07050504129. Archived from the original on 2014-02-02. Retrieved 2009-06-29.
  7. ^ van der Plicht, Johannes; Hogg, Alan (2006). "A note on reporting radiocarbon" (PDF). Quaternary Geochronology. 1 (4): 237–240. Bibcode:2006QuGeo...1..237V. doi:10.1016/j.quageo.2006.07.001. S2CID 128628228.
  8. ^ "The use of time units in Quaternary Science Reviews". Quaternary Science Reviews. 26 (9–10): 1193. May 2007. Bibcode:2007QSRv...26.1193.. doi:10.1016/j.quascirev.2007.04.002.
  9. ^ Wolff, Eric W. (December 2007). "When is the "present"?". Quaternary Science Reviews. 26 (25–28): 3023–3024. Bibcode:2007QSRv...26.3023W. doi:10.1016/j.quascirev.2007.10.008. S2CID 131227900.
  10. ^ Edward J. Huth (25 November 1994). Scientific Style and Format: The CBE Manual for Authors, Editors, and Publishers. Cambridge University Press. pp. 495–. ISBN 978-0-521-47154-1. Retrieved 4 October 2012.
  11. ^ "The GICC05 time scale". Centre for Ice and Climate – University of Copenhagen. 3 September 2009. Archived from the original on 18 September 2018. Retrieved September 17, 2018.
  12. ^ Berger, André (1988). "Milankovitch Theory and Climate". Reviews of Geophysics. 26 (4): 624–657. Bibcode:1988RvGeo..26..624B. doi:10.1029/RG026i004p00624. ISSN 8755-1209.
  13. ^ Martin Kölling (2015). "Numerous ways to say "thousand years" in a scientific paper". Universität Bremen: Marine Geochemistry - Laboratory Methods. Retrieved 2023-03-24.
  14. ^ Arnold, J.R.; Libby, W.F. (1949). "Age determinations by radiocarbon content: checks with samples of known age". Science. 110 (2869): 678–680. Bibcode:1949Sci...110..678A. doi:10.1126/science.110.2869.678. JSTOR 1677049. PMID 15407879.
  15. ^ Aitken (1990), pp. 60–61.
  16. ^ Currie, Lloyd A (March–April 2004). "The Remarkable Metrological History of Radiocarbon Dating [II]" (PDF). Journal of Research of the National Institute of Standards and Technology. 109 (2): 185–217. doi:10.6028/jres.109.013. PMC 4853109. PMID 27366605. Archived from the original (PDF) on 2010-12-06. Retrieved 30 October 2019. "The Remarkable Metrological History of Radiocarbon Dating [II]" Archived 2023-01-01 at the Wayback Machine at Google Books (accessed 30 October 2019).
  17. ^ Arnold JR, Libby WF (1949-03-04). "Age determinations by radiocarbon content: Checks with samples of known age". Science. 109 (2827): 227–228. Bibcode:1949Sci...109..227L. doi:10.1126/science.109.2827.227. PMID 17818054.
  18. ^ "Nuclear Bombs Made It Possible to Carbon Date Human Tissue". Smithsonian Magazine. 2013-02-19. Retrieved 2020-01-09.
  19. ^ Greene, Kevin (2002). Archaeology: An Introduction. Philadelphia: University of Pennsylvania Press. pp. 165–167. ISBN 0-8122-1828-0.
  20. ^ Walker, Mike; Jonsen, Sigfus; Rasmussen, Sune Olander; Popp, Trevor; Steffensen, Jørgen-Peder; Gibbard, Phil; Hoek, Wim; Lowe, John; Andrews, John; Björck, Svante; Cwynar, Les C.; Hughen, Konrad; Kershaw, Peter; Kromer, Bernd; Litt, Thomas; Lowe, David J.; Nakagawa, Takeshi; Newnham, Rewi; Schwander, Jacob (2009). "Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records" (PDF). Journal of Quaternary Science. 24 (1): 3–17. Bibcode:2009JQS....24....3W. doi:10.1002/jqs.1227. Archived (PDF) from the original on 2013-11-04.
  21. ^ a b Dershowitz, Nachum; Reingold, Edward M. (2008). Calendrical Calculations (3rd ed.). Cambridge University Press. ISBN 978-0-521-70238-6.
  22. ^ "ICS chart containing the Quaternary and Cambrian GSSPs and new stages (v 2018/07) is now released!". Retrieved February 6, 2019.
  23. ^ Conners, Deanna (September 18, 2018). "Welcome to the Meghalayan age". Retrieved February 6, 2019.
  24. ^ Currie Lloyd A (2004). "The Remarkable Metrological History of Radiocarbon Dating [II]" (PDF). Journal of Research of the National Institute of Standards and Technology. 109 (2): 185–217. doi:10.6028/jres.109.013. PMC 4853109. PMID 27366605. Archived from the original (PDF) on 2010-12-06. Retrieved 2018-06-24.

Sources

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