Given its current definition that depends on time(NULL), timetz_zone

is certainly no longer immutable, but must indeed be marked volatile.
I wonder if it should use the value of now() (that is, transaction
start time) so that it could be marked stable.  But it's probably not
important enough to be worth changing the code for ... indeed, I'm not
even going to force an initdb for this catalog change, seeing that we
just did one a few hours ago.

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.383 2005/08/13 19:02:34 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.384 2005/09/09 06:51:12 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -2959,7 +2959,7 @@ DATA(insert OID = 2035 (  timestamp_smaller PGNSP PGUID 12 f f t f i 2 1114 "111
 DESCR("smaller of two");
 DATA(insert OID = 2036 (  timestamp_larger	PGNSP PGUID 12 f f t f i 2 1114 "1114 1114" _null_ _null_ _null_	timestamp_larger - _null_ ));
 DESCR("larger of two");
-DATA(insert OID = 2037 (  timezone			PGNSP PGUID 12 f f t f i 2 1266 "25 1266" _null_ _null_ _null_  timetz_zone - _null_ ));
+DATA(insert OID = 2037 (  timezone			PGNSP PGUID 12 f f t f v 2 1266 "25 1266" _null_ _null_ _null_  timetz_zone - _null_ ));
 DESCR("adjust time with time zone to new zone");
 DATA(insert OID = 2038 (  timezone			PGNSP PGUID 12 f f t f i 2 1266 "1186 1266" _null_ _null_ _null_	timetz_izone - _null_ ));
 DESCR("adjust time with time zone to new zone");