diff --git a/doc/src/sgml/datetime.sgml b/doc/src/sgml/datetime.sgml
index 2cfda15f097..f5af88f134d 100644
--- a/doc/src/sgml/datetime.sgml
+++ b/doc/src/sgml/datetime.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/datetime.sgml,v 2.47 2005/09/09 02:31:48 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/datetime.sgml,v 2.47.2.1 2007/03/14 17:38:21 tgl Exp $
 -->
 
  <appendix id="datetime-appendix">
@@ -2230,24 +2230,33 @@ $PostgreSQL: pgsql/doc/src/sgml/datetime.sgml,v 2.47 2005/09/09 02:31:48 tgl Exp
 
    <para>
     In addition to the names listed in the table,
-    <productname>PostgreSQL</productname> will accept time zone names of the
-    form <replaceable>STD</><replaceable>offset</> or
+    <productname>PostgreSQL</productname> will accept POSIX-style time zone
+    specifications of the form <replaceable>STD</><replaceable>offset</> or
     <replaceable>STD</><replaceable>offset</><replaceable>DST</>, where
     <replaceable>STD</> is a zone abbreviation, <replaceable>offset</> is a
     numeric offset in hours west from UTC, and <replaceable>DST</> is an
-    optional daylight-savings zone abbreviation, assumed to stand for one hour
-    ahead of the given offset.  For example, if <literal>EST5EDT</> were not
-    already a recognized zone name, it would be accepted and would be
-    functionally equivalent to USA East Coast time.  When a daylight-savings
-    zone name is present, it is assumed to be used according to USA time zone
-    rules, so this feature is of limited use outside North America.
-    One should also be wary that this provision can lead to
-    silently accepting bogus input, since there is no check on the
-    reasonableness of the zone abbreviations.  For example,
-    <literal>SET TIMEZONE TO FOOBAR0</> will work, leaving the system
-    effectively using a rather peculiar abbreviation for GMT.
+    optional daylight-savings zone abbreviation, assumed to stand for one
+    hour ahead of the given offset. For example, if <literal>EST5EDT</>
+    were not already a recognized zone name, it would be accepted and would
+    be functionally equivalent to USA East Coast time.  When a
+    daylight-savings zone name is present, it is assumed to be used
+    according to the same daylight-savings transition rules used in the
+    <literal>zic</> time zone database's <filename>posixrules</> entry.
+    In a standard <productname>PostgreSQL</productname> installation,
+    <filename>posixrules</> is the same as <literal>US/Eastern</>, so
+    that POSIX-style time zone specifications follow USA daylight-savings
+    rules.  If needed, you can adjust this behavior by replacing the
+    <filename>posixrules</> file.
    </para>
 
+    <para>
+     One should be wary that the POSIX-style time zone feature can
+     lead to silently accepting bogus input, since there is no check on the
+     reasonableness of the zone abbreviations.  For example, <literal>SET
+     TIMEZONE TO FOOBAR0</> will work, leaving the system effectively using
+     a rather peculiar abbreviation for UTC.
+    </para>
+
   </sect1>
 
   <sect1 id="datetime-units-history">
diff --git a/src/timezone/Makefile b/src/timezone/Makefile
index a171035d8a8..2851558d300 100644
--- a/src/timezone/Makefile
+++ b/src/timezone/Makefile
@@ -4,7 +4,7 @@
 #    Makefile for the timezone library
 
 # IDENTIFICATION
-#    $PostgreSQL: pgsql/src/timezone/Makefile,v 1.22 2005/07/06 21:40:09 momjian Exp $
+#    $PostgreSQL: pgsql/src/timezone/Makefile,v 1.22.2.1 2007/03/14 17:38:22 tgl Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -25,6 +25,10 @@ TZDATA := africa antarctica asia australasia europe northamerica southamerica \
 	pacificnew etcetera factory backward systemv solar87 solar88 solar89
 TZDATAFILES := $(TZDATA:%=$(srcdir)/data/%)
 
+# which zone should determine the DST rules (not the specific UTC offset!)
+# for POSIX-style timezone specs
+POSIXRULES = US/Eastern
+
 all: SUBSYS.o submake-libpgport zic
 
 SUBSYS.o: $(OBJS)
@@ -34,7 +38,7 @@ zic: $(ZICOBJS)
 	$(CC) $(CFLAGS) $(ZICOBJS) $(LDFLAGS) $(LIBS) -o $@$(X)
 
 install: all installdirs
-	./zic -d $(DESTDIR)$(datadir)/timezone $(TZDATAFILES)
+	./zic -d $(DESTDIR)$(datadir)/timezone -p $(POSIXRULES) $(TZDATAFILES)
 
 installdirs:
 	$(mkinstalldirs) $(DESTDIR)$(datadir)