diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 1fa9cff5f7b..49efdbeb615 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6234,6 +6234,15 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
       </para>
      </listitem>
 
+     <listitem>
+      <para>
+       In <function>to_timestamp</function> and <function>to_date</function>,
+       negative years are treated as signifying BC.  If you write both a
+       negative year and an explicit <literal>BC</literal> field, you get AD
+       again.  An input of year zero is treated as 1 BC.
+      </para>
+     </listitem>
+
      <listitem>
       <para>
        In <function>to_timestamp</function> and <function>to_date</function>,
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 1b4cefadd68..0238df605ca 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -3733,8 +3733,11 @@ do_to_timestamp(text *date_txt, text *fmt,
 		{
 			/* If a 4-digit year is provided, we use that and ignore CC. */
 			tm->tm_year = tmfc.year;
-			if (tmfc.bc && tm->tm_year > 0)
-				tm->tm_year = -(tm->tm_year - 1);
+			if (tmfc.bc)
+				tm->tm_year = -tm->tm_year;
+			/* correct for our representation of BC years */
+			if (tm->tm_year < 0)
+				tm->tm_year++;
 		}
 		fmask |= DTK_M(YEAR);
 	}
diff --git a/src/test/regress/expected/horology.out b/src/test/regress/expected/horology.out
index 08cdfa1251c..d8c3650d116 100644
--- a/src/test/regress/expected/horology.out
+++ b/src/test/regress/expected/horology.out
@@ -2981,6 +2981,45 @@ SELECT to_date('2458872', 'J');
  01-23-2020
 (1 row)
 
+--
+-- Check handling of BC dates
+--
+SELECT to_date('44-02-01 BC','YYYY-MM-DD BC');
+    to_date    
+---------------
+ 02-01-0044 BC
+(1 row)
+
+SELECT to_date('-44-02-01','YYYY-MM-DD');
+    to_date    
+---------------
+ 02-01-0044 BC
+(1 row)
+
+SELECT to_date('-44-02-01 BC','YYYY-MM-DD BC');
+  to_date   
+------------
+ 02-01-0044
+(1 row)
+
+SELECT to_timestamp('44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+          to_timestamp           
+---------------------------------
+ Fri Feb 01 11:12:13 0044 PST BC
+(1 row)
+
+SELECT to_timestamp('-44-02-01 11:12:13','YYYY-MM-DD HH24:MI:SS');
+          to_timestamp           
+---------------------------------
+ Fri Feb 01 11:12:13 0044 PST BC
+(1 row)
+
+SELECT to_timestamp('-44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+         to_timestamp         
+------------------------------
+ Mon Feb 01 11:12:13 0044 PST
+(1 row)
+
 --
 -- Check handling of multiple spaces in format and/or input
 --
@@ -3168,6 +3207,12 @@ SELECT to_date('2016 366', 'YYYY DDD');  -- ok
 
 SELECT to_date('2016 367', 'YYYY DDD');
 ERROR:  date/time field value out of range: "2016 367"
+SELECT to_date('0000-02-01','YYYY-MM-DD');  -- allowed, though it shouldn't be
+    to_date    
+---------------
+ 02-01-0001 BC
+(1 row)
+
 --
 -- Check behavior with SQL-style fixed-GMT-offset time zone (cf bug #8572)
 --
diff --git a/src/test/regress/sql/horology.sql b/src/test/regress/sql/horology.sql
index c57d3197402..bfb8e2d6f37 100644
--- a/src/test/regress/sql/horology.sql
+++ b/src/test/regress/sql/horology.sql
@@ -461,6 +461,17 @@ SELECT to_date('1 4 1902', 'Q MM YYYY');  -- Q is ignored
 SELECT to_date('3 4 21 01', 'W MM CC YY');
 SELECT to_date('2458872', 'J');
 
+--
+-- Check handling of BC dates
+--
+
+SELECT to_date('44-02-01 BC','YYYY-MM-DD BC');
+SELECT to_date('-44-02-01','YYYY-MM-DD');
+SELECT to_date('-44-02-01 BC','YYYY-MM-DD BC');
+SELECT to_timestamp('44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+SELECT to_timestamp('-44-02-01 11:12:13','YYYY-MM-DD HH24:MI:SS');
+SELECT to_timestamp('-44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+
 --
 -- Check handling of multiple spaces in format and/or input
 --
@@ -529,6 +540,7 @@ SELECT to_date('2015 366', 'YYYY DDD');
 SELECT to_date('2016 365', 'YYYY DDD');  -- ok
 SELECT to_date('2016 366', 'YYYY DDD');  -- ok
 SELECT to_date('2016 367', 'YYYY DDD');
+SELECT to_date('0000-02-01','YYYY-MM-DD');  -- allowed, though it shouldn't be
 
 --
 -- Check behavior with SQL-style fixed-GMT-offset time zone (cf bug #8572)