diff --git a/mysql-test/r/func_sapdb.result b/mysql-test/r/func_sapdb.result
index cf2bd687115..c74d6fc5a4e 100644
--- a/mysql-test/r/func_sapdb.result
+++ b/mysql-test/r/func_sapdb.result
@@ -97,13 +97,16 @@ timediff("1997-12-31 23:59:59.000001","1997-12-30 01:01:01.000002")
 46:58:57.999999
 select timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002");
 timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002")
--23:59:59.999999
+-24:00:00.000001
 select timediff("1997-12-31 23:59:59.000001","23:59:59.000001");
 timediff("1997-12-31 23:59:59.000001","23:59:59.000001")
 NULL
 select timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001");
 timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001")
 -00:00:00.000001
+select timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50");
+timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50")
+-00:00:00.000001
 select maketime(10,11,12);
 maketime(10,11,12)
 10:11:12
@@ -175,7 +178,7 @@ f8	date	YES		NULL
 f9	time	YES		NULL	
 select * from t1;
 f1	f2	f3	f4	f5	f6	f7	f8	f9
-1997-01-01	1998-01-02 01:01:00	49:01:01	46:58:57	-23:59:59	10:11:12	2001-12-01 01:01:01	1997-12-31	23:59:59
+1997-01-01	1998-01-02 01:01:00	49:01:01	46:58:57	-24:00:00	10:11:12	2001-12-01 01:01:01	1997-12-31	23:59:59
 create table test(t1 datetime, t2 time, t3 time, t4 datetime);
 insert into test values 
 ('2001-01-01 01:01:01', '01:01:01', null, '2001-02-01 01:01:01'),
diff --git a/mysql-test/r/type_timestamp.result b/mysql-test/r/type_timestamp.result
index 42fdc7e50c6..6c46d308e7e 100644
--- a/mysql-test/r/type_timestamp.result
+++ b/mysql-test/r/type_timestamp.result
@@ -422,3 +422,13 @@ max(t)
 2004-01-01 01:00:00
 2004-02-01 00:00:00
 drop table t1;
+set sql_mode='maxdb';
+create table t1 (a timestamp, b timestamp(19));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE "t1" (
+  "a" datetime default NULL,
+  "b" datetime default NULL
+)
+set sql_mode='';
+drop table t1;
diff --git a/mysql-test/t/func_sapdb.test b/mysql-test/t/func_sapdb.test
index 2ae3c438243..de433485fca 100644
--- a/mysql-test/t/func_sapdb.test
+++ b/mysql-test/t/func_sapdb.test
@@ -54,6 +54,7 @@ select timediff("1997-12-31 23:59:59.000001","1997-12-30 01:01:01.000002");
 select timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002");
 select timediff("1997-12-31 23:59:59.000001","23:59:59.000001");
 select timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001");
+select timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50");
 --enable_ps_protocol
 
 select maketime(10,11,12);
diff --git a/mysql-test/t/type_timestamp.test b/mysql-test/t/type_timestamp.test
index a8a0cf8703c..783e310f02d 100644
--- a/mysql-test/t/type_timestamp.test
+++ b/mysql-test/t/type_timestamp.test
@@ -286,3 +286,15 @@ insert into t1 values ('a', '2004-01-01 00:00:00'), ('a', '2004-01-01 01:00:00')
                       ('b', '2004-02-01 00:00:00');
 select max(t) from t1 group by a;
 drop table t1;
+
+#
+# Test for bug #7418 "TIMESTAMP not always converted to DATETIME in MAXDB
+# mode". TIMESTAMP columns should be converted DATETIME columns in MAXDB
+# mode regardless of whether a display width is given.
+#
+set sql_mode='maxdb';
+create table t1 (a timestamp, b timestamp(19));
+show create table t1;
+# restore default mode
+set sql_mode='';
+drop table t1;
diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index 0d652a431cb..f9c9d1f013d 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -2432,8 +2432,7 @@ void Item_func_add_time::print(String *str)
 String *Item_func_timediff::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
-  longlong seconds;
-  long microseconds;
+  longlong microseconds;
   long days;
   int l_sign= 1;
   TIME l_time1 ,l_time2, l_time3;
@@ -2457,32 +2456,23 @@ String *Item_func_timediff::val_str(String *str)
 			     (uint) l_time2.month,
 			     (uint) l_time2.day));
 
-  microseconds= l_time1.second_part - l_sign*l_time2.second_part;
-  seconds= ((longlong) days*86400L + l_time1.hour*3600L + 
-	    l_time1.minute*60L + l_time1.second + microseconds/1000000L -
-	    (longlong)l_sign*(l_time2.hour*3600L+l_time2.minute*60L+
-			      l_time2.second));
+  microseconds= ((longlong)days*86400L +
+                 l_time1.hour*3600L + l_time1.minute*60L + l_time1.second -
+                 (longlong)l_sign*(l_time2.hour*3600L + l_time2.minute*60L +
+                                   l_time2.second))*1000000 +
+                 l_time1.second_part - l_sign*l_time2.second_part;
 
   l_time3.neg= 0;
-  if (seconds < 0)
-  {
-    seconds= -seconds;
-    l_time3.neg= 1;
-  }
-  else if (seconds == 0 && microseconds < 0)
+  if (microseconds < 0)
   {
     microseconds= -microseconds;
     l_time3.neg= 1;
   }
-  if (microseconds < 0)
-  {
-    microseconds+= 1000000L;
-    seconds--;
-  }
-  if ((l_time2.neg == l_time1.neg) && l_time1.neg)
+  if ((l_time2.neg == l_time1.neg) && l_time1.neg && microseconds)
     l_time3.neg= l_time3.neg ? 0 : 1;
 
-  calc_time_from_sec(&l_time3, (long) seconds, microseconds);
+  calc_time_from_sec(&l_time3, (long)(microseconds/1000000),
+                               (long)(microseconds%1000000));
 
   if (!make_datetime(l_time1.second_part || l_time2.second_part ?
 		     TIME_MICROSECOND : TIME_ONLY,
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 9235ce1fb6d..4fcc72bc90e 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -1415,7 +1415,7 @@ type:
 	| YEAR_SYM opt_len field_options { $$=FIELD_TYPE_YEAR; }
 	| DATE_SYM			{ $$=FIELD_TYPE_DATE; }
 	| TIME_SYM			{ $$=FIELD_TYPE_TIME; }
-	| TIMESTAMP
+	| TIMESTAMP opt_len
 	  {
 	    if (YYTHD->variables.sql_mode & MODE_MAXDB)
 	      $$=FIELD_TYPE_DATETIME;
@@ -1428,13 +1428,6 @@ type:
 	      $$=FIELD_TYPE_TIMESTAMP;
             }
 	   }
-	| TIMESTAMP '(' NUM ')'
-          { 
-            LEX *lex= Lex;
-            lex->length= $3.str;
-            lex->type|= NOT_NULL_FLAG;
-            $$= FIELD_TYPE_TIMESTAMP;
-          }
 	| DATETIME			{ $$=FIELD_TYPE_DATETIME; }
 	| TINYBLOB			{ Lex->charset=&my_charset_bin;
 					  $$=FIELD_TYPE_TINY_BLOB; }