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 |
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B.C. (Before Common Era) |
C.E. (Common Era) |
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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:
651 #0 $aRome$xHistory$yRepublic, 265-30 B.C.
045 ## $ad7d9
650 #0 $aBronze age.
045 ## $aa-c-
[3000-1000 B.C.]
651 #0 $aEgypt$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:
651 #0 $aGreat Britain$xHistory$yMedieval period, 1066-1485.
045 ## $ao6s8
650 #0 $aBhopal Union Carbide Plant Disaster, Bhopal, India, 1984.
045 ## $ax8x8
650 #0 $aCivilization, Modern$y20th century.
045 ## $ax-x-
650 #0 $aCatalan literature$y16th-18th centuries.
045 ## $at-v-
651 #0 $aGreece$xHistory$y146 B.C.-323 A.D.
045 ## $ad8h2
650 #0 $aTwenty-first century$xForecasts.
045 ## $ay-y-
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