> > I have no idea if this in Oracle or not. But it's something I

> > needed, and other people in the past asked about it too.
>
> It is in Oracle, but you aren't exactly on the spot.  It should be
>
> IYYY - 4 digits  ('2003')
> IYY  - 3 digits  ('003')
> IY   - 2 digits  ('03')
> I    - 1 digit   ('3')

Here is an updated patch that does that.

Kurt Roeckx

doc/src/sgml/func.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.183 2003/12/18 03:59:07 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.184 2003/12/25 03:36:23 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -3983,6 +3983,22 @@ substring('foobar' from 'o(.)b')   <lineannotation>o</lineannotation>
 	<entry><literal>Y</literal></entry>
 	<entry>last digit of year</entry>
        </row>
+       <row>
+	<entry><literal>IYYY</literal></entry>
+	<entry>ISO year (4 and more digits)</entry>
+       </row>
+       <row>
+	<entry><literal>IYY</literal></entry>
+	<entry>last 3 digits of ISO year</entry>
+       </row>
+       <row>
+	<entry><literal>IY</literal></entry>
+	<entry>last 2 digits of ISO year</entry>
+       </row>
+       <row>
+	<entry><literal>I</literal></entry>
+	<entry>last digits of ISO year</entry>
+       </row>
        <row>
 	<entry><literal>BC</literal> or <literal>B.C.</literal> or
 	<literal>AD</literal> or <literal>A.D.</literal></entry>

src/backend/utils/adt/formatting.c

 /* -----------------------------------------------------------------------
  * formatting.c
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/formatting.c,v 1.70 2003/11/29 19:51:58 pgsql Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/formatting.c,v 1.71 2003/12/25 03:36:23 momjian Exp $
  *
  *
  *	 Portions Copyright (c) 1999-2003, PostgreSQL Global Development Group
@@ -525,6 +525,10 @@ typedef enum
 	DCH_HH12,
 	DCH_HH,
 	DCH_IW,
+	DCH_IYYY,
+	DCH_IYY,
+	DCH_IY,
+	DCH_I,
 	DCH_J,
 	DCH_MI,
 	DCH_MM,
@@ -565,6 +569,10 @@ typedef enum
 	DCH_hh12,
 	DCH_hh,
 	DCH_iw,
+	DCH_iyyy,
+	DCH_iyy,
+	DCH_iy,
+	DCH_i,
 	DCH_j,
 	DCH_mi,
 	DCH_mm,
@@ -659,6 +667,10 @@ static KeyWord DCH_keywords[] = {
 	{"HH12", 4, dch_time, DCH_HH12, TRUE},
 	{"HH", 2, dch_time, DCH_HH, TRUE},
 	{"IW", 2, dch_date, DCH_IW, TRUE},	/* I */
+	{"IYYY", 4, dch_date, DCH_IYYY, TRUE},
+	{"IYY", 3, dch_date, DCH_IYY, TRUE},
+	{"IY", 2, dch_date, DCH_IY, TRUE},
+	{"I", 1, dch_date, DCH_I, TRUE},
 	{"J", 1, dch_date, DCH_J, TRUE},	/* J */
 	{"MI", 2, dch_time, DCH_MI, TRUE},
 	{"MM", 2, dch_date, DCH_MM, TRUE},
@@ -699,6 +711,10 @@ static KeyWord DCH_keywords[] = {
 	{"hh12", 4, dch_time, DCH_HH12, TRUE},
 	{"hh", 2, dch_time, DCH_HH, TRUE},
 	{"iw", 2, dch_date, DCH_IW, TRUE},	/* i */
+	{"iyyy", 4, dch_date, DCH_IYYY, TRUE},
+	{"iyy", 3, dch_date, DCH_IYY, TRUE},
+	{"iy", 2, dch_date, DCH_IY, TRUE},
+	{"i", 1, dch_date, DCH_I, TRUE},
 	{"j", 1, dch_time, DCH_J, TRUE},	/* j */
 	{"mi", 2, dch_time, DCH_MI, TRUE},	/* m */
 	{"mm", 2, dch_date, DCH_MM, TRUE},
@@ -2447,12 +2463,26 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			break;
 		case DCH_YYYY:
+		case DCH_IYYY:
 			if (flag == TO_CHAR)
 			{
 				if (tm->tm_year <= 9999 && tm->tm_year >= -9998)
-					sprintf(inout, "%0*d", S_FM(suf) ? 0 : 4, YEAR_ABS(tm->tm_year));
+					sprintf(inout, "%0*d",
+						S_FM(suf) ? 0 : 4,
+						arg == DCH_YYYY ?
+						YEAR_ABS(tm->tm_year) :
+						YEAR_ABS(date2isoyear(
+							tm->tm_year,
+							tm->tm_mon,
+							tm->tm_mday)));
 				else
-					sprintf(inout, "%d", YEAR_ABS(tm->tm_year));
+					sprintf(inout, "%d",
+						arg == DCH_YYYY ?
+						YEAR_ABS(tm->tm_year) :
+						YEAR_ABS(date2isoyear(
+							tm->tm_year,
+							tm->tm_mon,
+							tm->tm_mday)));
 				if (S_THth(suf))
 					str_numth(p_inout, inout, S_TH_TYPE(suf));
 				return strlen(p_inout) - 1;
@@ -2472,9 +2502,14 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			break;
 		case DCH_YYY:
+		case DCH_IYY:
 			if (flag == TO_CHAR)
 			{
-				snprintf(buff, sizeof(buff), "%03d", YEAR_ABS(tm->tm_year));
+				snprintf(buff, sizeof(buff), "%03d",
+					arg == DCH_YYY ?
+					YEAR_ABS(tm->tm_year) :
+					YEAR_ABS(date2isoyear(tm->tm_year,
+						tm->tm_mon, tm->tm_mday)));
 				i = strlen(buff);
 				strcpy(inout, buff + (i - 3));
 				if (S_THth(suf))
@@ -2502,9 +2537,14 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			break;
 		case DCH_YY:
+		case DCH_IY:
 			if (flag == TO_CHAR)
 			{
-				snprintf(buff, sizeof(buff), "%02d", YEAR_ABS(tm->tm_year));
+				snprintf(buff, sizeof(buff), "%02d",
+					arg == DCH_YY ?
+					YEAR_ABS(tm->tm_year) :
+					YEAR_ABS(date2isoyear(tm->tm_year,
+						tm->tm_mon, tm->tm_mday)));
 				i = strlen(buff);
 				strcpy(inout, buff + (i - 2));
 				if (S_THth(suf))
@@ -2532,9 +2572,14 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			break;
 		case DCH_Y:
+		case DCH_I:
 			if (flag == TO_CHAR)
 			{
-				snprintf(buff, sizeof(buff), "%1d", YEAR_ABS(tm->tm_year));
+				snprintf(buff, sizeof(buff), "%1d",
+					arg == DCH_Y ?
+					YEAR_ABS(tm->tm_year) :
+					YEAR_ABS(date2isoyear(tm->tm_year,
+						tm->tm_mon, tm->tm_mday)));
 				i = strlen(buff);
 				strcpy(inout, buff + (i - 1));
 				if (S_THth(suf))

src/backend/utils/adt/timestamp.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.97 2003/11/29 19:51:59 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.98 2003/12/25 03:36:23 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2840,7 +2840,7 @@ interval_trunc(PG_FUNCTION_ARGS)
 
 /* isoweek2date()
  * Convert ISO week of year number to date.
- * The year field must be specified!
+ * The year field must be specified with the ISO year!
  * karel 2000/08/07
  */
 void
@@ -2920,6 +2920,64 @@ date2isoweek(int year, int mon, int mday)
 }
 
 
+/* date2isoyear()
+ *
+ *	Returns ISO 8601 year number.
+ */
+int
+date2isoyear(int year, int mon, int mday)
+{
+	float8	result;
+	int	day0,
+		day4,
+		dayn;
+
+	/* current day */
+	dayn = date2j(year, mon, mday);
+
+	/* fourth day of current year */
+	day4 = date2j(year, 1, 4);
+
+	/* day0 == offset to first day of week (Monday) */
+	day0 = j2day(day4 - 1);
+
+	/*
+	 * We need the first week containing a Thursday, otherwise this day
+	 * falls into the previous year for purposes of counting weeks
+	 */
+	if (dayn < (day4 - day0))
+	{
+		day4 = date2j(year - 1, 1, 4);
+
+		/* day0 == offset to first day of week (Monday) */
+		day0 = j2day(day4 - 1);
+
+		year--;
+	}
+
+	result = (((dayn - (day4 - day0)) / 7) + 1);
+
+	/*
+	 * Sometimes the last few days in a year will fall into the first week
+	 * of the next year, so check for this.
+	 */
+	if (result >= 53)
+	{
+		day4 = date2j(year + 1, 1, 4);
+
+		/* day0 == offset to first day of week (Monday) */
+		day0 = j2day(day4 - 1);
+
+		if (dayn >= (day4 - day0))
+		{
+			year++;
+		}
+	}
+
+	return year;
+}
+
+
 /* timestamp_part()
  * Extract specified field from timestamp.
  */

src/include/utils/timestamp.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/timestamp.h,v 1.32 2003/11/29 22:41:16 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/utils/timestamp.h,v 1.33 2003/12/25 03:36:24 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -248,5 +248,6 @@ extern void GetEpochTime(struct tm * tm);
 
 extern void isoweek2date(int woy, int *year, int *mon, int *mday);
 extern int	date2isoweek(int year, int mon, int mday);
+extern int	date2isoyear(int year, int mon, int mday);
 
 #endif   /* TIMESTAMP_H */

src/test/regress/expected/timestamptz.out

@@ -1317,6 +1317,76 @@ SELECT '' AS to_char_9, to_char(d1, 'YYYY A.D. YYYY a.d. YYYY bc HH:MI:SS P.M. H
            | 2001 A.D. 2001 a.d. 2001 ad 05:32:01 P.M. 05:32:01 p.m. 05:32:01 pm
 (64 rows)
 
+SELECT '' AS to_char_10, to_char(d1, 'YYYY WW IYYY IYY IY I IW')
+   FROM TIMESTAMPTZ_TBL;
+ to_char_10 |     to_char
+------------+--------------------------
+            | 
+            | 
+            | 1969 53 1970 970 70 0 01
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 01 1997 997 97 7 01
+            | 1997 01 1997 997 97 7 01
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 23 1997 997 97 7 24
+            | 2001 38 2001 001 01 1 38
+            | 2000 11 2000 000 00 0 11
+            | 2000 11 2000 000 00 0 11
+            | 2000 11 2000 000 00 0 11
+            | 2000 11 2000 000 00 0 11
+            | 2000 11 2000 000 00 0 11
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 23 1997 997 97 7 24
+            | 1997 06 1997 997 97 7 07
+            | 1997 06 1997 997 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 0097 07 0097 097 97 7 07
+            | 0097 07 0097 097 97 7 07
+            | 0597 07 0597 597 97 7 07
+            | 1097 07 1097 097 97 7 07
+            | 1697 07 1697 697 97 7 07
+            | 1797 07 1797 797 97 7 07
+            | 1897 07 1897 897 97 7 07
+            | 1997 07 1997 997 97 7 07
+            | 2097 07 2097 097 97 7 07
+            | 1996 09 1996 996 96 6 09
+            | 1996 09 1996 996 96 6 09
+            | 1996 09 1996 996 96 6 09
+            | 1996 53 1997 997 97 7 01
+            | 1996 53 1997 997 97 7 01
+            | 1997 01 1997 997 97 7 01
+            | 1997 09 1997 997 97 7 09
+            | 1997 09 1997 997 97 7 09
+            | 1997 52 1998 998 98 8 01
+            | 1997 53 1998 998 98 8 01
+            | 1999 53 1999 999 99 9 52
+            | 2000 01 1999 999 99 9 52
+            | 2000 53 2000 000 00 0 52
+            | 2001 01 2001 001 01 1 01
+(64 rows)
+
 -- TO_TIMESTAMP()
 SELECT '' AS to_timestamp_1, to_timestamp('0097/Feb/16 --> 08:14:30', 'YYYY/Mon/DD --> HH:MI:SS');
  to_timestamp_1 |       to_timestamp       
@@ -1402,4 +1472,16 @@ SELECT '' AS to_timestamp_14, to_timestamp('995-1116', 'YYY-MMDD');
                  | Thu Nov 16 00:00:00 1995 PST
 (1 row)
 
+SELECT '' AS to_timestamp_15, to_timestamp('200401', 'IYYYIW');
+ to_timestamp_15 |         to_timestamp         
+-----------------+------------------------------
+                 | Mon Dec 29 00:00:00 2003 PST
+(1 row)
+
+SELECT '' AS to_timestamp_16, to_timestamp('200401', 'YYYYWW');
+ to_timestamp_16 |         to_timestamp         
+-----------------+------------------------------
+                 | Thu Jan 01 00:00:00 2004 PST
+(1 row)
+
 SET DateStyle TO DEFAULT;

src/test/regress/sql/timestamptz.sql

@@ -189,6 +189,9 @@ SELECT '' AS to_char_8, to_char(d1, 'YYYYTH YYYYth Jth')
 SELECT '' AS to_char_9, to_char(d1, 'YYYY A.D. YYYY a.d. YYYY bc HH:MI:SS P.M. HH:MI:SS p.m. HH:MI:SS pm') 
    FROM TIMESTAMPTZ_TBL;   
 
+SELECT '' AS to_char_10, to_char(d1, 'YYYY WW IYYY IYY IY I IW') 
+   FROM TIMESTAMPTZ_TBL;
+
 -- TO_TIMESTAMP()
 SELECT '' AS to_timestamp_1, to_timestamp('0097/Feb/16 --> 08:14:30', 'YYYY/Mon/DD --> HH:MI:SS');
 	
@@ -220,4 +223,9 @@ SELECT '' AS to_timestamp_13, to_timestamp('95-1116', 'YY-MMDD');
 
 SELECT '' AS to_timestamp_14, to_timestamp('995-1116', 'YYY-MMDD');
 
+SELECT '' AS to_timestamp_15, to_timestamp('200401', 'IYYYIW');
+
+SELECT '' AS to_timestamp_16, to_timestamp('200401', 'YYYYWW');
+
+
 SET DateStyle TO DEFAULT;