diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 19d357651786157e5b26e1f2f4c057704df0a7ba..139c81effc3727ab630bef56727ee9f6547601b2 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,5 +1,5 @@
<!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.196 2004/03/30 15:53:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.197 2004/04/10 18:02:59 momjian Exp $
PostgreSQL documentation
-->
@@ -4948,18 +4948,31 @@ EXTRACT (<replaceable>field</replaceable> FROM <replaceable>source</replaceable>
<term><literal>century</literal></term>
<listitem>
<para>
- The year field divided by 100
+ The historical definition of a century.
</para>
<screen>
-SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40');
+SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13');
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
+SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40');
+<lineannotation>Result: </lineannotation><computeroutput>21</computeroutput>
</screen>
<para>
- Note that the result for the century field is simply the year field
- divided by 100, and not the conventional definition which puts most
- years in the 1900's in the twentieth century.
+ An historical century is a period of 100 years.
+ The first century starts at 0001-01-01 00:00:00 AD, although
+ they did not know at the time. This definition applies to all
+ Gregorian calendar countries. There is no number 0 century,
+ you go from -1 to 1.
+
+ If you disagree with this, please write your complaint to:
+ Pope, Cathedral Saint-Peter of Roma, Vatican.
+ </para>
+
+ <para>
+ Compatibility: if you want the previous postgres version of century,
+ just divide the year by 100. Note that with this definition,
+ century number 0 lasts 200 years.
</para>
</listitem>
</varlistentry>
@@ -5083,18 +5096,17 @@ SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5');
<term><literal>millennium</literal></term>
<listitem>
<para>
- The year field divided by 1000
+ The conventional historical millennium.
</para>
<screen>
SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40');
-<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput>
+<lineannotation>Result: </lineannotation><computeroutput>3</computeroutput>
</screen>
<para>
- Note that the result for the millennium field is simply the year field
- divided by 1000, and not the conventional definition which puts
- years in the 1900's in the second millennium.
+ Years in the 1900's are in the second millennium.
+ The third millennium starts January 1, 2001.
</para>
</listitem>
</varlistentry>
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index dafc8ae5bedace622f141063ac7d7a4b17b28f8f..b2628a3a6f6aa4ea8fea63951607cf6175c5191a 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.103 2004/03/30 15:53:18 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.104 2004/04/10 18:02:59 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -3273,11 +3273,23 @@ timestamp_part(PG_FUNCTION_ARGS)
break;
case DTK_CENTURY:
- result = (tm->tm_year / 100);
+ /* centuries AD, c>0: year in [ (c-1)*100+1 : c*100 ]
+ * centuries BC, c<0: year in [ c*100 : (c+1)*100-1 ]
+ * there is no number 0 century.
+ */
+ if (tm->tm_year > 0)
+ result = ((tm->tm_year+99) / 100);
+ else
+ /* caution: C division may yave negative remainder */
+ result = - ((99 - (tm->tm_year-1))/100);
break;
case DTK_MILLENNIUM:
- result = (tm->tm_year / 1000);
+ /* see comments above. */
+ if (tm->tm_year > 0)
+ result = ((tm->tm_year+999) / 1000);
+ else
+ result = - ((999 - (tm->tm_year-1))/1000);
break;
case DTK_JULIAN:
diff --git a/src/test/regress/expected/date.out b/src/test/regress/expected/date.out
index 20ffaf188defcab7fabf24b1aca855a38b59ab8e..77bbdb967624ef745babdb83f95250fed8822dd2 100644
--- a/src/test/regress/expected/date.out
+++ b/src/test/regress/expected/date.out
@@ -819,3 +819,114 @@ SELECT date 'tomorrow' - date 'yesterday' AS "Two days";
2
(1 row)
+--
+-- test extract!
+--
+-- century
+--
+SELECT EXTRACT(CENTURY FROM DATE '0101-12-31 BC'); -- -2
+ date_part
+-----------
+ -2
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '0100-12-31 BC'); -- -1
+ date_part
+-----------
+ -1
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC'); -- -1
+ date_part
+-----------
+ -1
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '0001-01-01'); -- 1
+ date_part
+-----------
+ 1
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD'); -- 1
+ date_part
+-----------
+ 1
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '1900-12-31'); -- 19
+ date_part
+-----------
+ 19
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '1901-01-01'); -- 20
+ date_part
+-----------
+ 20
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '2000-12-31'); -- 20
+ date_part
+-----------
+ 20
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM DATE '2001-01-01'); -- 21
+ date_part
+-----------
+ 21
+(1 row)
+
+SELECT EXTRACT(CENTURY FROM CURRENT_DATE)>=21 AS True; -- true
+ true
+------
+ t
+(1 row)
+
+--
+-- millennium
+--
+SELECT EXTRACT(MILLENNIUM FROM DATE '0001-12-31 BC'); -- -1
+ date_part
+-----------
+ -1
+(1 row)
+
+SELECT EXTRACT(MILLENNIUM FROM DATE '0001-01-01 AD'); -- 1
+ date_part
+-----------
+ 1
+(1 row)
+
+SELECT EXTRACT(MILLENNIUM FROM DATE '1000-12-31'); -- 1
+ date_part
+-----------
+ 1
+(1 row)
+
+SELECT EXTRACT(MILLENNIUM FROM DATE '1001-01-01'); -- 2
+ date_part
+-----------
+ 2
+(1 row)
+
+SELECT EXTRACT(MILLENNIUM FROM DATE '2000-12-31'); -- 2
+ date_part
+-----------
+ 2
+(1 row)
+
+SELECT EXTRACT(MILLENNIUM FROM DATE '2001-01-01'); -- 3
+ date_part
+-----------
+ 3
+(1 row)
+
+-- next test to be fixed on the turn of the next millennium;-)
+SELECT EXTRACT(MILLENNIUM FROM CURRENT_DATE); -- 3
+ date_part
+-----------
+ 3
+(1 row)
+
diff --git a/src/test/regress/sql/date.sql b/src/test/regress/sql/date.sql
index 10bd87cadcf39a11f28d6503217112bdfbc0618b..a3cad66ed2e16d95f8ee41be25ff8fa383d8e8e6 100644
--- a/src/test/regress/sql/date.sql
+++ b/src/test/regress/sql/date.sql
@@ -208,3 +208,30 @@ SELECT date 'tomorrow' - date 'today' AS "One day";
SELECT date 'today' - date 'yesterday' AS "One day";
SELECT date 'tomorrow' - date 'yesterday' AS "Two days";
+
+--
+-- test extract!
+--
+-- century
+--
+SELECT EXTRACT(CENTURY FROM DATE '0101-12-31 BC'); -- -2
+SELECT EXTRACT(CENTURY FROM DATE '0100-12-31 BC'); -- -1
+SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC'); -- -1
+SELECT EXTRACT(CENTURY FROM DATE '0001-01-01'); -- 1
+SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD'); -- 1
+SELECT EXTRACT(CENTURY FROM DATE '1900-12-31'); -- 19
+SELECT EXTRACT(CENTURY FROM DATE '1901-01-01'); -- 20
+SELECT EXTRACT(CENTURY FROM DATE '2000-12-31'); -- 20
+SELECT EXTRACT(CENTURY FROM DATE '2001-01-01'); -- 21
+SELECT EXTRACT(CENTURY FROM CURRENT_DATE)>=21 AS True; -- true
+--
+-- millennium
+--
+SELECT EXTRACT(MILLENNIUM FROM DATE '0001-12-31 BC'); -- -1
+SELECT EXTRACT(MILLENNIUM FROM DATE '0001-01-01 AD'); -- 1
+SELECT EXTRACT(MILLENNIUM FROM DATE '1000-12-31'); -- 1
+SELECT EXTRACT(MILLENNIUM FROM DATE '1001-01-01'); -- 2
+SELECT EXTRACT(MILLENNIUM FROM DATE '2000-12-31'); -- 2
+SELECT EXTRACT(MILLENNIUM FROM DATE '2001-01-01'); -- 3
+-- next test to be fixed on the turn of the next millennium;-)
+SELECT EXTRACT(MILLENNIUM FROM CURRENT_DATE); -- 3