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 C.E. time period (R) $c Formatted pre-9999 B.C. time period (R) $6 Linkage (NR) $8 Field link and sequence number (R)