src/backend/utils/adt/timestamp.c       | 14 +++++++++
 src/test/regress/expected/timestamp.out | 54 +++++++++++++++++++++++++++++++++
 src/test/regress/sql/timestamp.sql      | 34 +++++++++++++++++++++
 3 files changed, 102 insertions(+)

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index f619b56d6f..0fc468404f 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -3844,6 +3844,13 @@ timestamp_bin(PG_FUNCTION_ARGS)
 	tm_diff = timestamp - origin;
 	tm_delta = tm_diff - tm_diff % stride_usecs;
 
+	/*
+	 * Make sure the returned timestamp is at the start of the bin,
+	 * even if the origin is in the future.
+	 */
+	if (origin > timestamp && stride_usecs > 1)
+		tm_delta -= stride_usecs;
+
 	result = origin + tm_delta;
 
 	PG_RETURN_TIMESTAMP(result);
@@ -4015,6 +4022,13 @@ timestamptz_bin(PG_FUNCTION_ARGS)
 	tm_diff = timestamp - origin;
 	tm_delta = tm_diff - tm_diff % stride_usecs;
 
+	/*
+	 * Make sure the returned timestamp is at the start of the bin,
+	 * even if the origin is in the future.
+	 */
+	if (origin > timestamp && stride_usecs > 1)
+		tm_delta -= stride_usecs;
+
 	result = origin + tm_delta;
 
 	PG_RETURN_TIMESTAMPTZ(result);
diff --git a/src/test/regress/expected/timestamp.out b/src/test/regress/expected/timestamp.out
index 89a856bac9..2550e7d136 100644
--- a/src/test/regress/expected/timestamp.out
+++ b/src/test/regress/expected/timestamp.out
@@ -600,6 +600,60 @@ FROM (
  microsecond | 1 us     | t
 (7 rows)
 
+-- case 3: AD dates, origin > input
+SELECT
+  str,
+  interval,
+  date_trunc(str, ts) = date_bin(interval::interval, ts, timestamp '2020-03-02') AS equal
+FROM (
+  VALUES
+  ('week', '7 d'),
+  ('day', '1 d'),
+  ('hour', '1 h'),
+  ('minute', '1 m'),
+  ('second', '1 s'),
+  ('millisecond', '1 ms'),
+  ('microsecond', '1 us')
+) intervals (str, interval),
+(VALUES (timestamp '2020-02-29 15:44:17.71393')) ts (ts);
+     str     | interval | equal 
+-------------+----------+-------
+ week        | 7 d      | t
+ day         | 1 d      | t
+ hour        | 1 h      | t
+ minute      | 1 m      | t
+ second      | 1 s      | t
+ millisecond | 1 ms     | t
+ microsecond | 1 us     | t
+(7 rows)
+
+-- case 4: BC dates, origin > input
+SELECT
+  str,
+  interval,
+  date_trunc(str, ts) = date_bin(interval::interval, ts, timestamp '0055-06-17 BC') AS equal
+FROM (
+  VALUES
+  ('week', '7 d'),
+  ('day', '1 d'),
+  ('hour', '1 h'),
+  ('minute', '1 m'),
+  ('second', '1 s'),
+  ('millisecond', '1 ms'),
+  ('microsecond', '1 us')
+) intervals (str, interval),
+(VALUES (timestamp '0055-6-10 15:44:17.71393 BC')) ts (ts);
+     str     | interval | equal 
+-------------+----------+-------
+ week        | 7 d      | t
+ day         | 1 d      | t
+ hour        | 1 h      | t
+ minute      | 1 m      | t
+ second      | 1 s      | t
+ millisecond | 1 ms     | t
+ microsecond | 1 us     | t
+(7 rows)
+
 -- bin timestamps into arbitrary intervals
 SELECT
   interval,
diff --git a/src/test/regress/sql/timestamp.sql b/src/test/regress/sql/timestamp.sql
index 256b96163d..2fd954c20b 100644
--- a/src/test/regress/sql/timestamp.sql
+++ b/src/test/regress/sql/timestamp.sql
@@ -202,6 +202,40 @@ FROM (
 ) intervals (str, interval),
 (VALUES (timestamp '0055-6-10 15:44:17.71393 BC')) ts (ts);
 
+-- case 3: AD dates, origin > input
+SELECT
+  str,
+  interval,
+  date_trunc(str, ts) = date_bin(interval::interval, ts, timestamp '2020-03-02') AS equal
+FROM (
+  VALUES
+  ('week', '7 d'),
+  ('day', '1 d'),
+  ('hour', '1 h'),
+  ('minute', '1 m'),
+  ('second', '1 s'),
+  ('millisecond', '1 ms'),
+  ('microsecond', '1 us')
+) intervals (str, interval),
+(VALUES (timestamp '2020-02-29 15:44:17.71393')) ts (ts);
+
+-- case 4: BC dates, origin > input
+SELECT
+  str,
+  interval,
+  date_trunc(str, ts) = date_bin(interval::interval, ts, timestamp '0055-06-17 BC') AS equal
+FROM (
+  VALUES
+  ('week', '7 d'),
+  ('day', '1 d'),
+  ('hour', '1 h'),
+  ('minute', '1 m'),
+  ('second', '1 s'),
+  ('millisecond', '1 ms'),
+  ('microsecond', '1 us')
+) intervals (str, interval),
+(VALUES (timestamp '0055-6-10 15:44:17.71393 BC')) ts (ts);
+
 -- bin timestamps into arbitrary intervals
 SELECT
   interval,