045 Time Period of Content

The 045 tag contains a time period code and/or a formatted time period associated with the resource being cataloged.

Until now, all of the tags we have talked about have been applicable to all types of library materials and their usage has not varied depending on the material represented by the cataloging record. For example, an 019 tag has exactly the same meaning in a record for a book as it does in a record for a videotape or for an archival collection of papers. 

The contents of the 045 indicate different things depending on the format of material the record describes:

• Books and Continuing Resources: the time period depicted by the content of the resource
• Computer Files:  the time period covered by the data in the file
• Map: the time period associated with the place shown in the map, that is, the situation date
• Mixed Materials: the time period covered by the collection
• Scores and Sound Recordings: the time period or specific date of the composition
• Motion Pictures and Videorecordings: the time period associated with the content of the resource
• Photographs and Prints: the time period associated with the content of the graphic
• Artifacts (meaning a human-made object): the time period associated with the content of the artifact
• Naturally Occuring Objects: the time period in which the object originated 

BF&S includes details and examples for each format. We will focus here on Books and Continuing Resources (magazines, for example). In this case what you find in the 045 indicates the time period depicted by the content of the resource, so not when it was created but when it describes. This time period designation is only valid in some situations, however.

Do not use for any resource for which a chronological approach would not be a logical or common approach to the subject matter. Do not use for the following:

• Biography, unless a time period is specified on the piece or in a subject heading
• Collections or anthologies of literature, unless they indicate a clearly delineated time period
• Comprehensive histories of a subject or a country that cover more than 500 years
• Dictionaries, encyclopedias, glossaries, catalogs, and gazetteers intended to be nonhistorical in approach
• Genealogies and family histories
• Handbooks, manuals, and "how-to" books

Subfield a contains the four-character time period code. The first two characters represent the earliest period covered. The last two represent the latest period covered. If a single two-character code encompasses the entire period, you will see the same code twice. You will find these codes in a table in BF&S and you really can't understand the codes without referring to the table. B.C. and C.E. dates are handled in specific ways.

B.C. (Before Common Era) dates. Use a lowercase alphabetic character to represent the millennium and a digit to represent the century. If the century is not known, enter a hyphen instead of a digit. For example:

• The Bronze Age is coded  a-c-
• The Egyptian 18th Dynasty (approx. 1570-1320 B.C) is coded c4c6

C.E. (Common Era) dates. Use a lowercase alphabetic character to represent the century and a digit to represent the decade. If the decade is not known, enter a hyphen instead of a digit. If more than one time period code applies, enter each in a separate subfield a. For example:

• An event in 1984, the Bhopal Union Carbide disaster, for example, is coded x8x8
• The 21st century is coded y-y- 
  
• The Medieval period of British history (1066-1485) is coded o6s8

 Subfield b contains a specific time period formatted as yyyymmddhh preceded by code c for B.C. or code d for C.E. for time periods 9999 B.C. through C.E. time periods (earlier time periods use subfield c). The era and year are required. The month, day, and hour (based on the 24-hour clock) are optional. This may be used with or without a subfield a. Each specific time period is entered in a separate subfield b.

• An event occurring on February 6, 1936 would be coded "ǂb d19360206"
• The French Revolution (1791-1797) would be coded in 2 subfields b: "ǂb d1791 ǂb d1797"

Subfield c contains a formatted time period consisting of as many numeric characters as are needed to represent the number of years B.C. Enter each pre-9999 B.C. time period associated with the heading in a separate subfield.

• The Mesozoic period (250 to 70 million years ago) is coded: "ǂc 250000000 ǂc 70000000" 

This tag may only occur once in a record, though the subfields may be repeated. The first indicator tells you the "Type of time period in subfield b or subfield c." The values of this indicator distinguish among a single date/time, multiple single dates/times, and a range of dates/times.

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Since this is the last Tuesday of the month it is time for the March 2024 Tuesday Tags Review Quiz. 

This is a 5-question self-check that will give you a chance to see how much you have learned about MARC tags this month (or where you may want to go back and re-read).