diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 9a61f27674..2b4fe0cb59 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6175,7 +6175,7 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
         <entry>microsecond (000000-999999)</entry>
        </row>
        <row>
-        <entry><literal>SSSS</literal></entry>
+        <entry><literal>SSSS</literal>, <literal>SSSSS</literal></entry>
         <entry>seconds past midnight (0-86399)</entry>
        </row>
        <row>
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index c6f992bfc1..053affa5ce 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -626,6 +626,7 @@ typedef enum
 	DCH_PM,
 	DCH_Q,
 	DCH_RM,
+	DCH_SSSSS,
 	DCH_SSSS,
 	DCH_SS,
 	DCH_TZH,
@@ -678,6 +679,7 @@ typedef enum
 	DCH_pm,
 	DCH_q,
 	DCH_rm,
+	DCH_sssss,
 	DCH_ssss,
 	DCH_ss,
 	DCH_tz,
@@ -787,7 +789,8 @@ static const KeyWord DCH_keywords[] = {
 	{"PM", 2, DCH_PM, false, FROM_CHAR_DATE_NONE},
 	{"Q", 1, DCH_Q, true, FROM_CHAR_DATE_NONE}, /* Q */
 	{"RM", 2, DCH_RM, false, FROM_CHAR_DATE_GREGORIAN}, /* R */
-	{"SSSS", 4, DCH_SSSS, true, FROM_CHAR_DATE_NONE},	/* S */
+	{"SSSSS", 5, DCH_SSSS, true, FROM_CHAR_DATE_NONE},	/* S */
+	{"SSSS", 4, DCH_SSSS, true, FROM_CHAR_DATE_NONE},
 	{"SS", 2, DCH_SS, true, FROM_CHAR_DATE_NONE},
 	{"TZH", 3, DCH_TZH, false, FROM_CHAR_DATE_NONE},	/* T */
 	{"TZM", 3, DCH_TZM, true, FROM_CHAR_DATE_NONE},
@@ -839,7 +842,8 @@ static const KeyWord DCH_keywords[] = {
 	{"pm", 2, DCH_pm, false, FROM_CHAR_DATE_NONE},
 	{"q", 1, DCH_Q, true, FROM_CHAR_DATE_NONE}, /* q */
 	{"rm", 2, DCH_rm, false, FROM_CHAR_DATE_GREGORIAN}, /* r */
-	{"ssss", 4, DCH_SSSS, true, FROM_CHAR_DATE_NONE},	/* s */
+	{"sssss", 5, DCH_SSSS, true, FROM_CHAR_DATE_NONE},	/* s */
+	{"ssss", 4, DCH_SSSS, true, FROM_CHAR_DATE_NONE},
 	{"ss", 2, DCH_SS, true, FROM_CHAR_DATE_NONE},
 	{"tz", 2, DCH_tz, false, FROM_CHAR_DATE_NONE},	/* t */
 	{"us", 2, DCH_US, true, FROM_CHAR_DATE_NONE},	/* u */
@@ -920,10 +924,10 @@ static const int DCH_index[KeyWord_INDEX_SIZE] = {
 	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 	-1, -1, -1, -1, -1, DCH_A_D, DCH_B_C, DCH_CC, DCH_DAY, -1,
 	DCH_FF1, -1, DCH_HH24, DCH_IDDD, DCH_J, -1, -1, DCH_MI, -1, DCH_OF,
-	DCH_P_M, DCH_Q, DCH_RM, DCH_SSSS, DCH_TZH, DCH_US, -1, DCH_WW, -1, DCH_Y_YYY,
+	DCH_P_M, DCH_Q, DCH_RM, DCH_SSSSS, DCH_TZH, DCH_US, -1, DCH_WW, -1, DCH_Y_YYY,
 	-1, -1, -1, -1, -1, -1, -1, DCH_a_d, DCH_b_c, DCH_cc,
 	DCH_day, -1, DCH_ff1, -1, DCH_hh24, DCH_iddd, DCH_j, -1, -1, DCH_mi,
-	-1, -1, DCH_p_m, DCH_q, DCH_rm, DCH_ssss, DCH_tz, DCH_us, -1, DCH_ww,
+	-1, -1, DCH_p_m, DCH_q, DCH_rm, DCH_sssss, DCH_tz, DCH_us, -1, DCH_ww,
 	-1, DCH_y_yyy, -1, -1, -1, -1
 
 	/*---- chars over 126 are skipped ----*/
diff --git a/src/test/regress/expected/horology.out b/src/test/regress/expected/horology.out
index 74ecb7c10e..6b53876e06 100644
--- a/src/test/regress/expected/horology.out
+++ b/src/test/regress/expected/horology.out
@@ -3077,6 +3077,14 @@ SELECT to_timestamp('2015-02-11 86000', 'YYYY-MM-DD SSSS');  -- ok
 
 SELECT to_timestamp('2015-02-11 86400', 'YYYY-MM-DD SSSS');
 ERROR:  date/time field value out of range: "2015-02-11 86400"
+SELECT to_timestamp('2015-02-11 86000', 'YYYY-MM-DD SSSSS');  -- ok
+         to_timestamp         
+------------------------------
+ Wed Feb 11 23:53:20 2015 PST
+(1 row)
+
+SELECT to_timestamp('2015-02-11 86400', 'YYYY-MM-DD SSSSS');
+ERROR:  date/time field value out of range: "2015-02-11 86400"
 SELECT to_date('2016-13-10', 'YYYY-MM-DD');
 ERROR:  date/time field value out of range: "2016-13-10"
 SELECT to_date('2016-02-30', 'YYYY-MM-DD');
@@ -3140,4 +3148,16 @@ SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD HH:MI:SS TZ');
  2012-12-12 12:00:00 -01:30
 (1 row)
 
+SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD SSSS');
+     to_char      
+------------------
+ 2012-12-12 43200
+(1 row)
+
+SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD SSSSS');
+     to_char      
+------------------
+ 2012-12-12 43200
+(1 row)
+
 RESET TIME ZONE;
diff --git a/src/test/regress/sql/horology.sql b/src/test/regress/sql/horology.sql
index 3c8580397a..f7a9da1e95 100644
--- a/src/test/regress/sql/horology.sql
+++ b/src/test/regress/sql/horology.sql
@@ -480,6 +480,8 @@ SELECT to_timestamp('2016-02-29 15:50:55', 'YYYY-MM-DD HH24:MI:SS');  -- ok
 SELECT to_timestamp('2015-02-29 15:50:55', 'YYYY-MM-DD HH24:MI:SS');
 SELECT to_timestamp('2015-02-11 86000', 'YYYY-MM-DD SSSS');  -- ok
 SELECT to_timestamp('2015-02-11 86400', 'YYYY-MM-DD SSSS');
+SELECT to_timestamp('2015-02-11 86000', 'YYYY-MM-DD SSSSS');  -- ok
+SELECT to_timestamp('2015-02-11 86400', 'YYYY-MM-DD SSSSS');
 SELECT to_date('2016-13-10', 'YYYY-MM-DD');
 SELECT to_date('2016-02-30', 'YYYY-MM-DD');
 SELECT to_date('2016-02-29', 'YYYY-MM-DD');  -- ok
@@ -503,5 +505,7 @@ SELECT '2012-12-12 12:00'::timestamptz;
 SELECT '2012-12-12 12:00 America/New_York'::timestamptz;
 
 SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD HH:MI:SS TZ');
+SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD SSSS');
+SELECT to_char('2012-12-12 12:00'::timestamptz, 'YYYY-MM-DD SSSSS');
 
 RESET TIME ZONE;