045 Subfield $a - Time Period Code:

Subfield $a contains a four-character alphanumeric code derived from the following Time Period Code Table for B.C. and C.E. time periods.  Each time period code associated with a heading is contained in a separate subfield $a.

Explanations and Examples of B.C. and C.E. dates follow the table.

Time Period Code Table

B.C. (Before Common Era)

C.E. (Common Era)

Code

Time Period

Code

Time Period

a0

before 2999

(Add 0, 1, 2 ... 9 to each alphabetic character for the decade.)

b0

2999-2900

e _

1-99

b1

2899-2800

f _

100-199

b2

2799-2700

g _

200-299

b3

2699-2600

h _

300-399

b4

2599-2500

i _

400-499

b5

2499-2400

j _

500-599

b6

2399-2300

k _

600-699

b7

2299-2200

l _

700-799

b8

2199-2100

m _

800-899

b9

2099-2000

n _

900-999

c0

1999-1900

o _

1000-1099

c1

1899-1800

p _

1100-1199

c2

1799-1700

q _

1200-1299

c3

1699-1600

r _

1300-1399

c4

1599-1500

s _

1400-1499

c5

1499-1400

t _

1500-1599

c6

1399-1300

u _

1600-1699

c7

1299-1200

v _

1700-1799

c8

1199-1100

w _

1800-1899

c9

1099-1000

x _

1900-1999

d0

999-900

y _

2000-2099

d1

899-800

 

 

d2

799-700

 

 

d3

699-600

 

 

d4

599-500

 

 

d5

499-400

 

 

d6

399-300

 

 

d7

299-200

 

 

d8

199-100

 

 

d9

99-1 

 

 

 

For B.C. dates, the lowercase alphabetic character represents the millennium and the digit represents the century.  If the century is not known, a hyphen ( - ) is used instead of a number.  A single century or a period within a century is coded by repeating the appropriate two-character code to create the required four-characters.

Examples:

151  ##  $aRome$xHistory$yRepublic, 265-30 B.C.

045  ##  $ad7d9

150  ##  $aBronze age

045  ##  $aa-c-

[3000-1000 B.C.]

151  ##  $aEgypt$xHistory$yEighteenth dynasty, ca. 1570-1320 B.C.

045  ##  $ac4c6

 

For C.E. dates, the lowercase alphabetic character represents the century.  A digit (0-9) is added to represent the decade.  If the decade is not known, a hyphen ( - ) is used instead of a number.  A single year or a period within a decade is coded by repeating the appropriate two-character code to create the required four characters.

Examples:

151  ##  $aGreat Britain$xHistory$yMedieval period, 1066-1485

045  ##  $ao6s8

150  ##  $aBhopal Union Carbide Plant Disaster, Bhopal, India, 1984

045  ##  $ax8x8

150  ##  $aCivilization, Modern$y20th century

045  ##  $ax-x-

150  ##  $aCatalan literature$y16th-18th centuries

045  ##  $at-v-

151  ##  $aGreece$xHistory$y146 B.C.-323 C.E.

045  ##  $ad8h2

150  ##  $aTwenty-first century$xForecasts

045  ##  $ay-y-

To return:

045  Time Period of Heading