diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 2a44b6e503..926358e6c9 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -103,8 +103,8 @@ static const datetkn datetktbl[] = {
 	{"d", UNITS, DTK_DAY},		/* "day of month" for ISO input */
 	{"dec", MONTH, 12},
 	{"december", MONTH, 12},
-	{"dow", RESERV, DTK_DOW},	/* day of week */
-	{"doy", RESERV, DTK_DOY},	/* day of year */
+	{"dow", UNITS, DTK_DOW},	/* day of week */
+	{"doy", UNITS, DTK_DOY},	/* day of year */
 	{"dst", DTZMOD, SECS_PER_HOUR},
 	{EPOCH, RESERV, DTK_EPOCH}, /* "epoch" reserved for system epoch time */
 	{"feb", MONTH, 2},
@@ -114,7 +114,7 @@ static const datetkn datetktbl[] = {
 	{"h", UNITS, DTK_HOUR},		/* "hour" */
 	{LATE, RESERV, DTK_LATE},	/* "infinity" reserved for "late time" */
 	{INVALID, RESERV, DTK_INVALID},		/* "invalid" reserved for bad time */
-	{"isodow", RESERV, DTK_ISODOW},		/* ISO day of week, Sunday == 7 */
+	{"isodow", UNITS, DTK_ISODOW},		/* ISO day of week, Sunday == 7 */
 	{"isoyear", UNITS, DTK_ISOYEAR},	/* year in terms of the ISO week date */
 	{"j", UNITS, DTK_JULIAN},
 	{"jan", MONTH, 1},
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 23d3d2b656..0c39a1ac02 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -4458,6 +4458,26 @@ timestamp_part(PG_FUNCTION_ARGS)
 				result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				break;
 
+			case DTK_DOW:
+			case DTK_ISODOW:
+				if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+							 errmsg("timestamp out of range")));
+				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
+				if (val == DTK_ISODOW && result == 0)
+					result = 7;
+				break;
+
+			case DTK_DOY:
+				if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+							 errmsg("timestamp out of range")));
+				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
+						  - date2j(tm->tm_year, 1, 1) + 1);
+				break;
+
 			case DTK_TZ:
 			case DTK_TZ_MINUTE:
 			case DTK_TZ_HOUR:
@@ -4481,26 +4501,6 @@ timestamp_part(PG_FUNCTION_ARGS)
 #endif
 				break;
 
-			case DTK_DOW:
-			case DTK_ISODOW:
-				if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-							 errmsg("timestamp out of range")));
-				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
-				if (val == DTK_ISODOW && result == 0)
-					result = 7;
-				break;
-
-			case DTK_DOY:
-				if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-							 errmsg("timestamp out of range")));
-				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
-						  - date2j(tm->tm_year, 1, 1) + 1);
-				break;
-
 			default:
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -4672,6 +4672,26 @@ timestamptz_part(PG_FUNCTION_ARGS)
 				result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				break;
 
+			case DTK_DOW:
+			case DTK_ISODOW:
+				if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+							 errmsg("timestamp out of range")));
+				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
+				if (val == DTK_ISODOW && result == 0)
+					result = 7;
+				break;
+
+			case DTK_DOY:
+				if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+							 errmsg("timestamp out of range")));
+				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
+						  - date2j(tm->tm_year, 1, 1) + 1);
+				break;
+
 			default:
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -4693,26 +4713,6 @@ timestamptz_part(PG_FUNCTION_ARGS)
 #endif
 				break;
 
-			case DTK_DOW:
-			case DTK_ISODOW:
-				if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-							 errmsg("timestamp out of range")));
-				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
-				if (val == DTK_ISODOW && result == 0)
-					result = 7;
-				break;
-
-			case DTK_DOY:
-				if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-							 errmsg("timestamp out of range")));
-				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
-						  - date2j(tm->tm_year, 1, 1) + 1);
-				break;
-
 			default:
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),