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

Time period code (subfield $a) and/or a formatted time period (subfield $b or $c) associated with a 15X heading in an established heading record or a 18X heading in a subdivision record.

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.

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

0 - Single date/time

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


150	##$aLunar petrology
045	0#$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 together express a range of dates and/or times. Multiple single dates and/or times are identified by value 1.


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


150	##$aAurignacian culture
045	2#$c25000$c15000

■ SUBFIELD CODES

$a - Time period code

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

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

Time Period Code Table

B.C. (Before Common Era)

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)

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

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.


151	#0$aRome$xHistory$yRepublic, 265-30 B.C.
045	##$ad7d9


150	#0$aBronze age
045	##$aa-c- [3000-1000 B.C.]


151	##$aEgypt$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.


151	#0$aGreat Britain$xHistory$yMedieval period, 1066-1485.
045	##$ao6s8


150	#0$aBhopal Union Carbide Plant Disaster, Bhopal, India, 1984.
045	##$ax8x8


150	#0$aCivilization, Modern$y20th century.
045	##$ax-x-


150	#0$aCatalan literature$y16th-18th centuries.
045	##$at-v-


151	##$aGreece$xHistory$y146 B.C.-323 C.E.
045	##$ad8h2


150	##$aTwenty-first century$xForecasts.
045	##$ay-y-

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

Specific time period formatted as yyyymmddhh, preceded by a code for the era (c for B.C.; d for C.E.).

Era and year are required components; the 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.


151	##$aFrance$xHistory$yRevolution, 1791-1797
045	2#$bd1791$bd1797


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


151	##$aChina$xHistory$y221 B.C.-960 C.E.
045	2#$ad7n6$bc0221$bd0960

$c - Formatted pre-9999 B.C. time period

Formatted time period that consists of as many numeric characters as are needed to represent the number of pre-9999 years B.C.

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


150	##$aGeology, Stratigraphic$yMesozoic
045	2#$c225000000$c70000000

045 - Time Period of Heading (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)