MARC 21 Format for Bibliographic Data: 045: Time Period of Content (Network Development and MARC Standards Office, Library of Congress)

Time period code (subfield $a) and/or a formatted time period (subfield $b and/or $c) associated with an item.

Time period code in subfield $a is derived from the B.C. (Before Common Era) and/or C.E. (Common Era) lists in the Time Period Code Table provided under the description of subfield $a.

For books and continuing resources, this field indicates the period depicted by the content of the item (e.g., history of the 16th century would be coded as 045 ##$at-t- or 045 2#$bd1500$bd1599).

For collections of mixed materials, this field indicates the time period covered by the collection.

For computer files, this field indicates the period covered by the data in the file (e.g., a data file containing statistics for the period 1950-1960 would be coded 045 ##$ax5x6).

For cartographic material, this field indicates the date portrayed on the item, that is, the situation date. A currently prepared map of Rome in 50 B.C. would be coded for the B.C. date. A remote-sensing map which depicts the time the satellite recorded the image would be coded for that time.

For printed music and sound recordings, this field indicates the period of the composition, and will usually relate to the date of the composition. If the precise date of composition cannot be determined, an approximate date (or range of dates) or the dates of the composer are used.

For motion pictures and videorecordings, this field indicates the time period depicted in the film (e.g., a videorecording documentary of the history of the brewing industry in Wisconsin for the period 1900-1986 would be coded 045 2#$bd1900$bd1986).

For two-dimensional nonprojectable graphic representations, this field indicates the time period depicted in the graphic (e.g., a collection of photographs from 1870 to 1930 would be coded 045 ##$aw7x3).

For artifacts, this field indicates the time period covered by the content of the artifact (e.g., a model of an automobile repair shop of the 1920-1930 period would be coded 045 ##$ax2x3).

For naturally occurring objects, this field indicates the time period of the content, that is, the time period that the item originated (e.g., a geode would be coded for the time period when it was formed).

GUIDELINES FOR APPLYING CONTENT DESIGNATORS

■ INDICATORS

First Indicator - Type of time period in subfield $b or $c

Whether a subfield $b or $c is present in the field and, when subfield $b or $c is present, the type of time period it contains. The values distinguish among a single date/time, multiple single dates/times, and a range of dates/times.

# - Subfield $b or $c not present

Neither subfield $b or $c is present.


651	#0$aEgypt$xEconomic conditions$yTo 332 B.C.
045	##$aa0d6

0 - Single date/time

Subfield $b and/or $c is present and contains a single date/time.


650	#0$aLunar petrology.
045	0#$c2500000000

1 - Multiple single dates/times

Multiple $b and/or $c subfields are present, each containing a date/time.A range of dates/times is identified by value 2.


045	1#$bd1972$bd1975 [1972 and 1975]

2 - Range of dates/times

Two $b and/or $c subfields are present and contain a range of dates/times.Multiple single dates and/or times are identified by value 1 (Multiple single dates/times).


650	#0$aShenandoah Valley Campaign, 1864 (May-August)
045	2#$bd186405$bd186408


650	#0$aAurignacian culture.
045	2#$c25000$c15000

■ SUBFIELD CODES

$a - Time period code

Four-character alphanumeric code derived from the "Time Period Code Table" for B.C. and A.D. time periods.

Table is found in MARC 21 Format for Bibliographic Data under the description of field 045.

Each time period code associated with a heading is contained in a separate subfield $a.

Time Period Code Table

B.C. (Before Common Era)

(Add 0, 1, 2, ... 9 to each alphabetic character for the decade)

Code	Time period
a0	before 2999
b0	2999-2900
b1	2899-2800
b2	2799-2700
b3	2699-2600
b4	2599-2500
b5	2499-2400
b6	2399-2300
b7	2299-2200
b8	2199-2100
b9	2099-2000
c0	1999-1900
c1	1899-1800
c2	1799-1700
c3	1699-1600
c4	1599-1500
c5	1499-1400
c6	1399-1300
c7	1299-1200
c8	1199-1100
c9	1099-1000
d0	999-900
d1	899-800
d2	799-700
d3	699-600
d4	599-500
d5	499-400
d6	399-300
d7	299-200
d8	199-100
d9	99-1

C.E. (Common Era)

Code	Time period
e	1-99
f	100-199
g	200-299
h	300-399
i	400-499
j	500-599
k	600-699
l	700-799
m	800-899
n	900-999
o	1000-1099
p	1100-1199
q	1200-1299
r	1300-1399
s	1400-1499
t	1500-1599
u	1600-1699
v	1700-1799
w	1800-1899
x	1900-1999
y	2000-2099

For B.C. dates, the lowercase alphabetic character represents the millennium and the digit represents the century. If the century is not known, a hyphen (-) is used instead of a number. A single century or a period within a century is coded by repeating the appropriate two-character code to create the required four-characters.


651	#0$aRome$xHistory$yRepublic, 265-30 B.C.
045	##$ad7d9


650	#0$aBronze age.
045	##$aa-c- [3000-1000 B.C.]


651	#0$aEgypt$xHistory$yEighteenth dynasty, ca. 1570-1320 B.C.
045	##$ac4c6

For C.E. dates, the lowercase alphabetic character represents the century. A digit (0-9) is added to represent the decade. If the decade is not known, a hyphen (-) is used instead of a number.

A single year or a period within a decade is coded by repeating the appropriate two-character code to create the required four characters.


651	#0$aGreat Britain$xHistory$yMedieval period, 1066-1485.
045	##$ao6s8


650	#0$aBhopal Union Carbide Plant Disaster, Bhopal, India, 1984.
045	##$ax8x8


650	#0$aCivilization, Modern$y20th century.
045	##$ax-x-


650	#0$aCatalan literature$y16th-18th centuries.
045	##$at-v-


651	#0$aGreece$xHistory$y146 B.C.-323 A.D.
045	##$ad8h2


650	#0$aTwenty-first century$xForecasts.
045	##$ay-y-

$b - Formatted 9999 B.C. through C.E. time period

Specific time period recorded in the pattern yyyymmddhh and preceded by a code for the era (c for B.C.; d for C.E.).

Era and year are required components; month, day, and hour are optional.

era expressed as a code: c (B.C.), d (C.E.)
year expressed as a four-digit number (0000 to 9999) right justified; unused positions contain zeros
month expressed as a two-digit number (01 to 12) right justified; unused positions contain zeros
day expressed as a two-digit number (01 to 31) right justified; unused positions contain zeros
hour expressed as a two-digit number using the 24-hour clock (00 to 23) right justified; unused positions contain zeros.

First indicator position values 0-2 specify whether the time period in subfield $b is a single date, multiple dates, or a range of dates. Each 9999 B.C. through C.E. time period associated with the heading is contained in a separate subfield $b.


651	#0$aFrance$xHistory$yRevolution, 1791-1797.
045	2#$bd1791$bd1797


651	#0$aJapan$xHistory$yFebruary Incident, 1936 (February 26)
045	0#$bd19360226


651	#0$aChina$xHistory$y221 B.C.-960 A.D.
045	2#$ad7n6$bc0221$bd0960

045 - Time Period of Content (NR)

FIELD DEFINITION AND SCOPE

GUIDELINES FOR APPLYING CONTENT DESIGNATORS

■ INDICATORS

■ SUBFIELD CODES

INPUT CONVENTIONS

CONTENT DESIGNATOR HISTORY


Subfield Codes
$a - Time period code (R) $b - Formatted 9999 B.C. through C.E. time period (R) $c - Formatted pre-9999 B.C. time period (R)	$6 - Linkage (NR) $8 - Field link and sequence number (R)


650	#0$aGeology, Stratigraphic$yMesozoic.
045	2#$c225000000$c70000000