diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 34fea16eee..ae22ee5f7f 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6684,8 +6684,10 @@ SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
       <term><literal>epoch</literal></term>
       <listitem>
        <para>
-        For <type>date</type> and <type>timestamp</type> values, the
+        For <type>timestamp with time zone</type> values, the
         number of seconds since 1970-01-01 00:00:00 UTC (can be negative);
+        for <type>date</type> and <type>timestamp</type> values, the
+        number of seconds since 1970-01-01 00:00:00 local time;
         for <type>interval</type> values, the total number
         of seconds in the interval
        </para>
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 9a7238be38..a3e1e94a2b 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -4066,32 +4066,13 @@ timestamp_part(PG_FUNCTION_ARGS)
 		switch (val)
 		{
 			case DTK_EPOCH:
-				{
-					int			tz;
-					TimestampTz timestamptz;
-
-					/*
-					 * convert to timestamptz to produce consistent results
-					 */
-					if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
-						ereport(ERROR,
-								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-								 errmsg("timestamp out of range")));
-
-					tz = DetermineTimeZoneOffset(tm, session_timezone);
-
-					if (tm2timestamp(tm, fsec, &tz, &timestamptz) != 0)
-						ereport(ERROR,
-								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-								 errmsg("timestamp out of range")));
-
 #ifdef HAVE_INT64_TIMESTAMP
-					result = (timestamptz - SetEpochTimestamp()) / 1000000.0;
+					result = (timestamp - SetEpochTimestamp()) / 1000000.0;
 #else
-					result = timestamptz - SetEpochTimestamp();
+					result = timestamp - SetEpochTimestamp();
 #endif
 					break;
-				}
+
 			case DTK_DOW:
 			case DTK_ISODOW:
 				if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)