045 TIME PERIOD OF CONTENT (NR)
Indicators 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; contains a blank (#)
Subfield Codes $a Time period code (R) $b Formatted 9999 B.C. through A.D. time period (R) $c Formatted pre-9999 B.C. time period (R)