diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 9ab070adffba..ccc5b9d7a255 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -24916,6 +24916,22 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_postmaster_open_time</primary>
+        </indexterm>
+        <function>pg_postmaster_open_time</function> ()
+        <returnvalue>timestamp with time zone</returnvalue>
+       </para>
+       <para>
+        Returns the time when the server was open to connections. On a standby
+        this will be the time when the server was open to read-only connections.
+        In single-user mode this returns the time the server was ready to accept
+        user commands.
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index bf6b55ee8304..bad35abfe6e8 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -111,6 +111,7 @@ typedef struct
 	ProcSignalHeader *ProcSignal;
 	pid_t		PostmasterPid;
 	TimestampTz PgStartTime;
+	TimestampTz PgOpenStartTime;
 	TimestampTz PgReloadTime;
 	pg_time_t	first_syslogger_file_time;
 	bool		redirection_done;
@@ -771,6 +772,7 @@ save_backend_variables(BackendParameters *param,
 
 	param->PostmasterPid = PostmasterPid;
 	param->PgStartTime = PgStartTime;
+	param->PgOpenStartTime = PgOpenStartTime;
 	param->PgReloadTime = PgReloadTime;
 	param->first_syslogger_file_time = first_syslogger_file_time;
 
@@ -1031,6 +1033,7 @@ restore_backend_variables(BackendParameters *param)
 
 	PostmasterPid = param->PostmasterPid;
 	PgStartTime = param->PgStartTime;
+	PgOpenStartTime = param->PgOpenStartTime;
 	PgReloadTime = param->PgReloadTime;
 	first_syslogger_file_time = param->first_syslogger_file_time;
 
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 17fed96fe20c..7a820997617a 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -2342,6 +2342,11 @@ process_pm_child_exit(void)
 			 */
 			StartWorkerNeeded = true;
 
+			/*
+			 * Remember time when database was open to connections
+			 */
+			PgOpenStartTime = GetCurrentTimestamp();
+
 			/* at this point we are really open for business */
 			ereport(LOG,
 					(errmsg("database system is ready to accept connections")));
@@ -3737,6 +3742,11 @@ process_pm_pmsignal(void)
 		ereport(LOG,
 				(errmsg("database system is ready to accept read-only connections")));
 
+		/*
+		 * Remember time when database was open to connections
+		 */
+		PgOpenStartTime = GetCurrentTimestamp();
+
 		/* Report status */
 		AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_READY);
 #ifdef USE_SYSTEMD
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 6ae9f38f0c84..ee9bfdd604cc 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -4157,6 +4157,11 @@ PostgresSingleUserMain(int argc, char *argv[],
 	 */
 	PgStartTime = GetCurrentTimestamp();
 
+	/*
+	 * Remember when stand-alone was open to user commands.
+	 */
+	PgOpenStartTime = GetCurrentTimestamp();
+
 	/*
 	 * Create a per-backend PGPROC struct in shared memory. We must do this
 	 * before we can use LWLocks.
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 347089b76264..0badfd215c97 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -53,6 +53,9 @@
 /* Set at postmaster start */
 TimestampTz PgStartTime;
 
+/* Set when database is open to connections */
+TimestampTz PgOpenStartTime;
+
 /* Set at configuration reload */
 TimestampTz PgReloadTime;
 
@@ -1629,6 +1632,12 @@ pg_postmaster_start_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(PgStartTime);
 }
 
+Datum
+pg_postmaster_open_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(PgOpenStartTime);
+}
+
 Datum
 pg_conf_load_time(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 37a484147a8f..b5155150a3a4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -8741,6 +8741,12 @@
   prorettype => 'timestamptz', proargtypes => '',
   prosrc => 'pg_postmaster_start_time' },
 
+# open to connections start time function
+{ oid => '8600', descr => 'open connections start time',
+  proname => 'pg_postmaster_open_time', provolatile => 's',
+  prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_postmaster_open_time' },
+
 # config reload time function
 { oid => '2034', descr => 'configuration load time',
   proname => 'pg_conf_load_time', provolatile => 's', proparallel => 'r',
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index 8c205859c3be..7960d15f37fe 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -98,6 +98,9 @@ TimestampDifferenceMicroseconds(TimestampTz start_time,
 /* Set at postmaster start */
 extern PGDLLIMPORT TimestampTz PgStartTime;
 
+/* Set when database is open to connections */
+extern PGDLLIMPORT TimestampTz PgOpenStartTime;
+
 /* Set at configuration reload */
 extern PGDLLIMPORT TimestampTz PgReloadTime;