045 - Time Period of Heading (NR)
MARC 21 Authority - Concise
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.
First - Type of time period in subfield $b or $c
# - Subfield $b or $c not present
0 - Single date/time
1 - Multiple single dates/times
2 - Range of dates/times
Second - Undefined
# - Undefined
$a - Time period code (R)
Four-character alphanumeric code derived from the "Time Period Code Table" for
B.C. and C.E. time periods.
$b - Formatted 9999 B.C. through C.E. time period (R)
Specific time period formatted as yyyymmddhh, preceded by a code for the
era (c for B.C.; d for C.E.).
$c - Formatted pre-9999 B.C. time period (R)
Formatted time period that consists of as many numeric characters as are needed to
represent the number of pre-9999 years B.C.
$8 - Field link and sequence number (R)