045 Time Period of Heading

Field definition and scope:

Field 045 contains a time period code (subfield $a) and/or a formatted time period (subfields $b or $c) associated with a 15X heading in an established heading record or an 18X heading in a subdivision record. The 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.

The National level record requirement for this field is Optional.

Field 045 is NOT repeatable.

Guidelines for applying content designators:

For indicator and subfield code definitions and examples, National level (NLR) record requirements, and designator repeatability, see table below:

Position	Description	NLR	Repeatability
Field 045	Time Period of Heading	O	NR
Indicator:
First	Type of time period in subfield $b or $c	M
#	Subfield $b or $c not present	A
0	Single date/time	A
1	Multiple single dates/times	A
2	Range of dates/times	A

Second	Undefined; contains a blank	M

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

Input conventions:

Punctuation

Order of subfields

Content designator history:

First Indicator - Type of time period in subfield $b or $c [new, 1979]

Subfields $b - Chronological date/time [new, 1979]

$b - 9999 B.C. through C.E. time period, formatted [redefined, 1987]

$c - Pre-9999 B.C. time period, formatted [new, 1987]

Subfield $b was redefined for 9999 B.C. through C.E. time periods when subfield $c was defined for pre-9999 B.C. time periods in 1987. Prior to that time, all dates/times were contained in subfield $b.

LC Guidelines:

045 Time Period of Heading