Re: [HACKERS] Dates BC.

Karel Zak wrote:
> On Fri, Dec 19, 2003 at 01:12:08AM -0800, Dann Corbit wrote:
> > There is no zero calendar year.  The first year of Anno Domini is 1.  It's ordinal, not cardinal.
>
>  I agree. But  the follow quoted  code is  not use in  date_part() there
>  Kurt  found bug. It's  used  in to_timestamp()  _only_,  and it  works,
>  because tm2timestamp() and date2j() work with zero year.

I have also add a doc mention to my patch that mentions that there is no
0 AD, and therefore subtraction of BC years from AD years must be done
with caution.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: doc/src/sgml/func.sgml
===================================================================
RCS file: /cvsroot/pgsql-server/doc/src/sgml/func.sgml,v
retrieving revision 1.195
diff -c -c -r1.195 func.sgml
*** doc/src/sgml/func.sgml    19 Mar 2004 19:13:26 -0000    1.195
--- doc/src/sgml/func.sgml    29 Mar 2004 20:31:28 -0000
***************
*** 5216,5223 ****
        <term><literal>week</literal></term>
        <listitem>
         <para>
!         The number of
!         the week of the year that the day is in.  By definition
          (<acronym>ISO</acronym> 8601), the first week of a year
          contains January 4 of that year.  (The <acronym>ISO</acronym>-8601
          week starts on Monday.)  In other words, the first Thursday of
--- 5216,5222 ----
        <term><literal>week</literal></term>
        <listitem>
         <para>
!         The number of the week of the year that the day is in.  By definition
          (<acronym>ISO</acronym> 8601), the first week of a year
          contains January 4 of that year.  (The <acronym>ISO</acronym>-8601
          week starts on Monday.)  In other words, the first Thursday of
***************
*** 5235,5241 ****
        <term><literal>year</literal></term>
        <listitem>
         <para>
!         The year field
         </para>

  <screen>
--- 5234,5241 ----
        <term><literal>year</literal></term>
        <listitem>
         <para>
!         The year field.  Keep in mind there is no <literal>0 AD</>, so subtracting
!         <literal>BC</> years from <literal>AD</> years should be done with care.
         </para>

  <screen>
Index: src/backend/utils/adt/datetime.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/adt/datetime.c,v
retrieving revision 1.125
diff -c -c -r1.125 datetime.c
*** src/backend/utils/adt/datetime.c    25 Feb 2004 19:41:23 -0000    1.125
--- src/backend/utils/adt/datetime.c    29 Mar 2004 20:31:34 -0000
***************
*** 93,99 ****
      {"acsst", DTZ, POS(42)},    /* Cent. Australia */
      {"acst", DTZ, NEG(16)},        /* Atlantic/Porto Acre Summer Time */
      {"act", TZ, NEG(20)},        /* Atlantic/Porto Acre Time */
!     {DA_D, ADBC, AD},            /* "ad" for years >= 0 */
      {"adt", DTZ, NEG(12)},        /* Atlantic Daylight Time */
      {"aesst", DTZ, POS(44)},    /* E. Australia */
      {"aest", TZ, POS(40)},        /* Australia Eastern Std Time */
--- 93,99 ----
      {"acsst", DTZ, POS(42)},    /* Cent. Australia */
      {"acst", DTZ, NEG(16)},        /* Atlantic/Porto Acre Summer Time */
      {"act", TZ, NEG(20)},        /* Atlantic/Porto Acre Time */
!     {DA_D, ADBC, AD},            /* "ad" for years > 0 */
      {"adt", DTZ, NEG(12)},        /* Atlantic Daylight Time */
      {"aesst", DTZ, POS(44)},    /* E. Australia */
      {"aest", TZ, POS(40)},        /* Australia Eastern Std Time */
***************
*** 139,145 ****
      {"azot", TZ, NEG(4)},        /* Azores Time */
      {"azst", DTZ, POS(20)},        /* Azerbaijan Summer Time */
      {"azt", TZ, POS(16)},        /* Azerbaijan Time */
!     {DB_C, ADBC, BC},            /* "bc" for years < 0 */
      {"bdst", TZ, POS(8)},        /* British Double Summer Time */
      {"bdt", TZ, POS(24)},        /* Dacca */
      {"bnt", TZ, POS(32)},        /* Brunei Darussalam Time */
--- 139,145 ----
      {"azot", TZ, NEG(4)},        /* Azores Time */
      {"azst", DTZ, POS(20)},        /* Azerbaijan Summer Time */
      {"azt", TZ, POS(16)},        /* Azerbaijan Time */
!     {DB_C, ADBC, BC},            /* "bc" for years <= 0 */
      {"bdst", TZ, POS(8)},        /* British Double Summer Time */
      {"bdt", TZ, POS(24)},        /* Dacca */
      {"bnt", TZ, POS(32)},        /* Brunei Darussalam Time */
Index: src/backend/utils/adt/formatting.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/adt/formatting.c,v
retrieving revision 1.72
diff -c -c -r1.72 formatting.c
*** src/backend/utils/adt/formatting.c    7 Jan 2004 18:56:28 -0000    1.72
--- src/backend/utils/adt/formatting.c    29 Mar 2004 20:31:40 -0000
***************
*** 169,175 ****
   * AC / DC
   * ----------
   */
! #define YEAR_ABS(_y)    (_y < 0 ? -(_y -1) : _y)
  #define BC_STR_ORIG " BC"

  #define A_D_STR        "A.D."
--- 169,175 ----
   * AC / DC
   * ----------
   */
! #define YEAR_ABS(_y)    (_y <= 0 ? -(_y -1) : _y)
  #define BC_STR_ORIG " BC"

  #define A_D_STR        "A.D."
***************
*** 2119,2125 ****
          case DCH_B_C:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year < 0 ? B_C_STR : A_D_STR));
                  return 3;

              }
--- 2119,2125 ----
          case DCH_B_C:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year <= 0 ? B_C_STR : A_D_STR));
                  return 3;

              }
***************
*** 2134,2140 ****
          case DCH_BC:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year < 0 ? BC_STR : AD_STR));
                  return 1;

              }
--- 2134,2140 ----
          case DCH_BC:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year <= 0 ? BC_STR : AD_STR));
                  return 1;

              }
***************
*** 2149,2155 ****
          case DCH_b_c:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year < 0 ? b_c_STR : a_d_STR));
                  return 3;

              }
--- 2149,2155 ----
          case DCH_b_c:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year <= 0 ? b_c_STR : a_d_STR));
                  return 3;

              }
***************
*** 2164,2170 ****
          case DCH_bc:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year < 0 ? bc_STR : ad_STR));
                  return 1;

              }
--- 2164,2170 ----
          case DCH_bc:
              if (flag == TO_CHAR)
              {
!                 strcpy(inout, (tm->tm_year <= 0 ? bc_STR : ad_STR));
                  return 1;

              }
Index: src/backend/utils/adt/timestamp.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.102
diff -c -c -r1.102 timestamp.c
*** src/backend/utils/adt/timestamp.c    22 Mar 2004 01:38:17 -0000    1.102
--- src/backend/utils/adt/timestamp.c    29 Mar 2004 20:31:44 -0000
***************
*** 3261,3267 ****
                  break;

              case DTK_YEAR:
!                 result = tm->tm_year;
                  break;

              case DTK_DECADE:
--- 3261,3271 ----
                  break;

              case DTK_YEAR:
!                 if (tm->tm_year > 0)
!                     result = tm->tm_year;
!                 else
!                     /* there is no year 0, just 1 BC and 1 AD*/
!                     result = tm->tm_year - 1;
                  break;

              case DTK_DECADE: