The following patches eliminate the overflows in the j2date() and date2j()

functions which limited the maximum date for a timestamp to AD 1465001.
The new limit is AD 5874897.
The files affected are:

doc/src/sgml/datatype.sgml:
    Documentation change due to patch. Included is a notice about
    the reduced range when using an eight-byte integer for timestamps.

src/backend/utils/adt/datetime.c:
    Replacement functions for j2date() and date2j() functions.

src/include/utils/datetime.h:
    Corrected a bug with the limit on the earliest possible date,
    Nov 23,-4713 has a Julian day count of -1. The earliest possible
    date should be Nov 24, -4713 with a day count of 0.

src/test/regress/expected/horology-no-DST-before-1970.out:
src/test/regress/expected/horology-solaris-1947.out:
src/test/regress/expected/horology.out:
    Copies of expected output for regression testing.
    Note: Only horology.out has been physically tested. I do not have access
    to a Solaris box and I don't know how to provoke the "pre-1970" test.

src/test/regress/sql/horology.sql:
    Added some test cases to check extended range.

John Cochran

src/test/regress/expected/horology-no-DST-before-1970.out

@@ -328,6 +328,30 @@ SELECT timestamp without time zone '1999-12-01' + interval '1 month - 1 second'
  Fri Dec 31 23:59:59 1999
 (1 row)
 
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '1000000000 days' AS "Nov 27, 2733194";
+       Nov 27, 2733194       
+-----------------------------
+ Sun Nov 27 00:00:00 2733194
+(1 row)
+
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '2000000000 days' AS "Nov 30, 5471101";
+       Nov 30, 5471101       
+-----------------------------
+ Sat Nov 30 00:00:00 5471101
+(1 row)
+
+SELECT timestamp without time zone 'Nov 25, 4714 BC' + interval '2147483492 days' AS "Dec 31, 5874897";
+       Dec 31, 5874897       
+-----------------------------
+ Tue Dec 31 00:00:00 5874897
+(1 row)
+
+SELECT timestamp without time zone '12/31/5874897' - timestamp without time zone 'Nov 24, 4714 BC' AS "2147483493 Days";
+  2147483493 Days  
+-------------------
+ @ 2147483493 days
+(1 row)
+
 -- Shorthand values
 -- Not directly usable for regression testing since these are not constants.
 -- So, just try to test parser and hope for the best - thomas 97/04/26

src/test/regress/expected/horology-solaris-1947.out

@@ -328,6 +328,30 @@ SELECT timestamp without time zone '1999-12-01' + interval '1 month - 1 second'
  Fri Dec 31 23:59:59 1999
 (1 row)
 
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '1000000000 days' AS "Nov 27, 2733194";
+       Nov 27, 2733194       
+-----------------------------
+ Sun Nov 27 00:00:00 2733194
+(1 row)
+
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '2000000000 days' AS "Nov 30, 5471101";
+       Nov 30, 5471101       
+-----------------------------
+ Sat Nov 30 00:00:00 5471101
+(1 row)
+
+SELECT timestamp without time zone 'Nov 25, 4714 BC' + interval '2147483492 days' AS "Dec 31, 5874897";
+       Dec 31, 5874897       
+-----------------------------
+ Tue Dec 31 00:00:00 5874897
+(1 row)
+
+SELECT timestamp without time zone '12/31/5874897' - timestamp without time zone 'Nov 24, 4714 BC' AS "2147483493 Days";
+  2147483493 Days  
+-------------------
+ @ 2147483493 days
+(1 row)
+
 -- Shorthand values
 -- Not directly usable for regression testing since these are not constants.
 -- So, just try to test parser and hope for the best - thomas 97/04/26

src/test/regress/expected/horology.out

@@ -328,6 +328,30 @@ SELECT timestamp without time zone '1999-12-01' + interval '1 month - 1 second'
  Fri Dec 31 23:59:59 1999
 (1 row)
 
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '1000000000 days' AS "Nov 27, 2733194";
+       Nov 27, 2733194       
+-----------------------------
+ Sun Nov 27 00:00:00 2733194
+(1 row)
+
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '2000000000 days' AS "Nov 30, 5471101";
+       Nov 30, 5471101       
+-----------------------------
+ Sat Nov 30 00:00:00 5471101
+(1 row)
+
+SELECT timestamp without time zone 'Nov 25, 4714 BC' + interval '2147483492 days' AS "Dec 31, 5874897";
+       Dec 31, 5874897       
+-----------------------------
+ Tue Dec 31 00:00:00 5874897
+(1 row)
+
+SELECT timestamp without time zone '12/31/5874897' - timestamp without time zone 'Nov 24, 4714 BC' AS "2147483493 Days";
+  2147483493 Days  
+-------------------
+ @ 2147483493 days
+(1 row)
+
 -- Shorthand values
 -- Not directly usable for regression testing since these are not constants.
 -- So, just try to test parser and hope for the best - thomas 97/04/26

src/test/regress/sql/horology.sql

@@ -76,6 +76,10 @@ SELECT timestamp without time zone '1996-03-01' - interval '1 second' AS "Feb 29
 SELECT timestamp without time zone '1999-03-01' - interval '1 second' AS "Feb 28";
 SELECT timestamp without time zone '2000-03-01' - interval '1 second' AS "Feb 29";
 SELECT timestamp without time zone '1999-12-01' + interval '1 month - 1 second' AS "Dec 31";
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '1000000000 days' AS "Nov 27, 2733194";
+SELECT timestamp without time zone 'Nov 24, 4714 BC' + interval '2000000000 days' AS "Nov 30, 5471101";
+SELECT timestamp without time zone 'Nov 25, 4714 BC' + interval '2147483492 days' AS "Dec 31, 5874897";
+SELECT timestamp without time zone '12/31/5874897' - timestamp without time zone 'Nov 24, 4714 BC' AS "2147483493 Days";
 
 -- Shorthand values
 -- Not directly usable for regression testing since these are not constants.