diff --git a/sql/cambios.sql b/sql/cambios.sql
index 92d76e3a0..6a003f277 100644
--- a/sql/cambios.sql
+++ b/sql/cambios.sql
@@ -11158,3 +11158,10 @@ OPTIMIZE TABLE ws_keys;
 -----
 
 SELECT TstCod,AllowTeachers,UNIX_TIMESTAMP(TstTime) AS T,NumQsts,NumQstsNotBlank,Score FROM tst_exams WHERE T>='0' AND T<='2000000000' ORDER BY TstCod;
+
+-----
+
+SELECT * FROM expanded_folders WHERE UNIX_TIMESTAMP() > UNIX_TIMESTAMP(ClickTime)+'1000';
+SELECT * FROM expanded_folders WHERE ClickTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'1000');
+
+
diff --git a/sql/swad.sql b/sql/swad.sql
index d6e2962ef..212040555 100644
--- a/sql/swad.sql
+++ b/sql/swad.sql
@@ -1,14 +1,6 @@
 CREATE DATABASE IF NOT EXISTS swad DEFAULT CHARACTER SET=latin1 DEFAULT COLLATE latin1_spanish_ci;
 USE swad;
 --
--- Table IP_last: stores the last click from each IP address
---
-CREATE TABLE IF NOT EXISTS IP_last (
-	IP CHAR(15) NOT NULL,
-	LastClick DATETIME NOT NULL,
-	PRIMARY KEY(IP),
-	INDEX(LastClick));
---
 -- Table IP_prefs: stores user's preferences for each IP address
 --
 CREATE TABLE IF NOT EXISTS IP_prefs (
diff --git a/swad_RSS.c b/swad_RSS.c
index b143b5d20..467164c86 100644
--- a/swad_RSS.c
+++ b/swad_RSS.c
@@ -156,7 +156,9 @@ static void RSS_WriteNotices (FILE *FileRSS,struct Course *Crs)
 
    /***** Get active notices in course *****/
    sprintf (Query,"SELECT NotCod,UNIX_TIMESTAMP(CreatTime) AS T,UsrCod,Content"
-                  " FROM notices WHERE CrsCod='%ld' AND Status='%u' ORDER BY T DESC",
+                  " FROM notices"
+                  " WHERE CrsCod='%ld' AND Status='%u'"
+                  " ORDER BY T DESC",
             Crs->CrsCod,(unsigned) Not_ACTIVE_NOTICE);
    NumNotices = DB_QuerySELECT (Query,&mysql_res,"can not get notices from database");
 
diff --git a/swad_changelog.h b/swad_changelog.h
index 72a430b4d..8484ede18 100644
--- a/swad_changelog.h
+++ b/swad_changelog.h
@@ -108,16 +108,23 @@
 // TODO: Row with total of users in figures
 // TODO: Remove total rows in listing of places
 // TODO: Show message indicating that mail could be in SPAM folder
+// TODO: Remove email address for recipients rejected (mailbox unavailable)
 
 /*****************************************************************************/
 /****************************** Public constants *****************************/
 /*****************************************************************************/
 
-#define Log_PLATFORM_VERSION	"SWAD 15.36 (2015/11/10)"
+#define Log_PLATFORM_VERSION	"SWAD 15.37 (2015/11/11)"
 
 // Number of lines (includes comments but not blank lines) has been got with the following command:
 // nl swad*.c swad*.h css/swad*.css py/swad*.py js/swad*.js soap/swad*.h sql/swad*.sql | tail -1
 /*
+        Version 15.37:    Nov 11, 2015	Changes to speed up queries related to time.
+					Time to next test printed in user's local time.
+					Table table IP_last removed. (186909 lines)
+					1 change necessary in database:
+DROP TABLE IF EXISTS IP_last;
+
         Version 15.36:    Nov 10, 2015	Fixed bug in assignments, reported by Javier Fernández Baldomero.
 					Changes in automatic creation of assignment folders. (186985 lines)
         Version 15.35.5:  Nov 09, 2015	Fixed bug in swad.sql, reported by Florent H. Carré.
diff --git a/swad_course.c b/swad_course.c
index ce0552f15..24f32dc77 100644
--- a/swad_course.c
+++ b/swad_course.c
@@ -3490,7 +3490,7 @@ void Crs_RemoveOldCrss (void)
 
    /***** Get old courses from database *****/
    sprintf (Query,"SELECT CrsCod FROM crs_last WHERE"
-                  " UNIX_TIMESTAMP(LastTime) < UNIX_TIMESTAMP()-%lu"
+                  " LastTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')"
                   " AND CrsCod NOT IN (SELECT DISTINCT CrsCod FROM crs_usr)",
             SecondsWithoutAccess);
    if ((NumCrss = DB_QuerySELECT (Query,&mysql_res,"can not get old users")))
diff --git a/swad_database.c b/swad_database.c
index 28ff665e8..639b7e229 100644
--- a/swad_database.c
+++ b/swad_database.c
@@ -85,22 +85,6 @@ void DB_CreateTablesIfNotExist (void)
    Lay_ShowAlert (Lay_INFO,Txt_Creating_database_tables_if_they_do_not_exist);
    fprintf (Gbl.F.Out,"<ol>");
 
-   /***** Table IP_last *****/
-/*
-mysql> DESCRIBE IP_last;
-+-----------+----------+------+-----+---------+-------+
-| Field     | Type     | Null | Key | Default | Extra |
-+-----------+----------+------+-----+---------+-------+
-| IP        | char(15) | NO   | PRI | NULL    |       |
-| LastClick | datetime | NO   | MUL | NULL    |       |
-+-----------+----------+------+-----+---------+-------+
-2 rows in set (0.00 sec)
-*/
-   DB_CreateTable ("CREATE TABLE IF NOT EXISTS IP_last ("
-                   "IP CHAR(15) NOT NULL,"
-                   "LastClick DATETIME NOT NULL,"
-                   "PRIMARY KEY(IP),INDEX(LastClick))");
-
    /***** Table IP_prefs *****/
 /*
 mysql> DESCRIBE IP_prefs;
diff --git a/swad_enrollment.c b/swad_enrollment.c
index eccf59882..e4cd993b1 100644
--- a/swad_enrollment.c
+++ b/swad_enrollment.c
@@ -744,7 +744,7 @@ void Enr_RemoveOldUsrs (void)
    sprintf (Query,"SELECT UsrCod FROM"
                   "("
                   "SELECT UsrCod FROM usr_last WHERE"
-                  " UNIX_TIMESTAMP(LastTime) < UNIX_TIMESTAMP()-%lu"
+                  " LastTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')"
                   " UNION "
                   "SELECT UsrCod FROM usr_data WHERE"
                   " UsrCod NOT IN (SELECT UsrCod FROM usr_last)"
diff --git a/swad_file_browser.c b/swad_file_browser.c
index ec4a4f3be..5f4d29095 100644
--- a/swad_file_browser.c
+++ b/swad_file_browser.c
@@ -7058,7 +7058,7 @@ void Brw_RemoveExpiredExpandedFolders (void)
 
    /***** Remove all expired clipboards *****/
    sprintf (Query,"DELETE LOW_PRIORITY FROM expanded_folders"
-                  " WHERE UNIX_TIMESTAMP() > UNIX_TIMESTAMP(ClickTime)+%ld",
+                  " WHERE ClickTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_BROWSER_EXPANDED_FOLDERS);
    DB_QueryDELETE (Query,"can not remove old expanded folders");
   }
@@ -7073,7 +7073,7 @@ static void Brw_RemoveExpiredClipboards (void)
 
    /***** Remove all expired clipboards *****/
    sprintf (Query,"DELETE LOW_PRIORITY FROM clipboard"
-                  " WHERE UNIX_TIMESTAMP() > UNIX_TIMESTAMP(CopyTime)+%ld",
+                  " WHERE CopyTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_BROWSER_CLIPBOARD);
    DB_QueryDELETE (Query,"can not remove old paths from clipboard");
   }
diff --git a/swad_forum.c b/swad_forum.c
index 35e372f76..93debfadd 100644
--- a/swad_forum.c
+++ b/swad_forum.c
@@ -1245,7 +1245,8 @@ static void For_GetPstData (long PstCod,long *UsrCod,time_t *CreatTimeUTC,
 
    /***** Get data of a post from database *****/
    sprintf (Query,"SELECT UsrCod,UNIX_TIMESTAMP(CreatTime),Subject,Content"
-                  " FROM forum_post WHERE PstCod='%ld'",PstCod);
+                  " FROM forum_post WHERE PstCod='%ld'",
+            PstCod);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get data of a post");
 
    /***** Result should have a unique row *****/
@@ -3427,7 +3428,9 @@ void For_GetThrData (struct ForumThread *Thr)
                   "UNIX_TIMESTAMP(m1.CreatTime),"
                   "m0.Subject"
                   " FROM forum_thread,forum_post AS m0,forum_post AS m1"
-                  " WHERE forum_thread.ThrCod='%ld' AND forum_thread.FirstPstCod=m0.PstCod AND forum_thread.LastPstCod=m1.PstCod",
+                  " WHERE forum_thread.ThrCod='%ld'"
+                  " AND forum_thread.FirstPstCod=m0.PstCod"
+                  " AND forum_thread.LastPstCod=m1.PstCod",
             Thr->ThrCod);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get data of a thread of a forum");
 
@@ -4208,7 +4211,7 @@ void For_RemoveExpiredThrsClipboards (void)
 
    /***** Remove all expired clipboards *****/
    sprintf (Query,"DELETE LOW_PRIORITY FROM forum_thr_clip"
-                  " WHERE UNIX_TIMESTAMP() > UNIX_TIMESTAMP(TimeInsert)+%ld",
+                  " WHERE TimeInsert<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_THREAD_CLIPBOARD);
    DB_QueryDELETE (Query,"can not remove old threads from clipboards");
   }
diff --git a/swad_group.c b/swad_group.c
index d59ca0513..5e50a98f3 100644
--- a/swad_group.c
+++ b/swad_group.c
@@ -2353,7 +2353,7 @@ void Grp_OpenGroupsAutomatically (void)
    /***** Find group types to be opened *****/
    sprintf (Query,"SELECT GrpTypCod FROM crs_grp_types"
 	          " WHERE CrsCod='%ld' AND MustBeOpened='Y'"
-	          " AND UNIX_TIMESTAMP(OpenTime)<=UNIX_TIMESTAMP()",
+	          " AND OpenTime<=NOW()",
 	    Gbl.CurrentCrs.Crs.CrsCod);
    NumGrpTypes = (unsigned) DB_QuerySELECT (Query,&mysql_res,
 	                                    "can not get the types of group to be opened");
diff --git a/swad_mail.c b/swad_mail.c
index 4ccd9907f..bd703a843 100644
--- a/swad_mail.c
+++ b/swad_mail.c
@@ -1269,7 +1269,7 @@ static void Mai_InsertMailKey (const char *Email,const char MailKey[Mai_LENGTH_E
 
    /***** Remove expired pending passwords from database *****/
    sprintf (Query,"DELETE FROM pending_emails"
-                  " WHERE (UNIX_TIMESTAMP() > UNIX_TIMESTAMP(DateAndTime)+'%ld')",
+                  " WHERE DateAndTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_OLD_PENDING_EMAILS);
    DB_QueryDELETE (Query,"can not remove old pending mail keys");
 
diff --git a/swad_message.c b/swad_message.c
index 48816dce4..43d67e769 100644
--- a/swad_message.c
+++ b/swad_message.c
@@ -2418,14 +2418,16 @@ static void Msg_GetMsgSntData (long MsgCod,long *CrsCod,long *UsrCod,
    /***** Get data of message from table msg_snt *****/
    *Deleted = false;
    sprintf (Query,"SELECT CrsCod,UsrCod,UNIX_TIMESTAMP(CreatTime)"
-                  " FROM msg_snt WHERE MsgCod='%ld'",MsgCod);
+                  " FROM msg_snt WHERE MsgCod='%ld'",
+            MsgCod);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get data of a message");
 
    if (NumRows == 0)   // If not result ==> sent message is deleted
      {
       /***** Get data of message from table msg_snt_deleted *****/
       sprintf (Query,"SELECT CrsCod,UsrCod,UNIX_TIMESTAMP(CreatTime)"
-                     " FROM msg_snt_deleted WHERE MsgCod='%ld'",MsgCod);
+                     " FROM msg_snt_deleted WHERE MsgCod='%ld'",
+               MsgCod);
       NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get data of a message");
 
       *Deleted = true;
diff --git a/swad_notification.c b/swad_notification.c
index a784283e7..9286c51ca 100644
--- a/swad_notification.c
+++ b/swad_notification.c
@@ -1279,7 +1279,7 @@ void Ntf_SendPendingNotifByEMailToAllUsrs (void)
    /***** Get users who must be notified from database ******/
    // (Status & Ntf_STATUS_BIT_EMAIL) && !(Status & Ntf_STATUS_BIT_SENT) && !(Status & (Ntf_STATUS_BIT_READ | Ntf_STATUS_BIT_REMOVED))
    sprintf (Query,"SELECT DISTINCT ToUsrCod FROM notif"
-                  " WHERE UNIX_TIMESTAMP(TimeNotif) < UNIX_TIMESTAMP()-%lu"
+                  " WHERE TimeNotif<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')"
                   " AND (Status & %u)<>0 AND (Status & %u)=0 AND (Status & %u)=0",
             Cfg_TIME_TO_SEND_PENDING_NOTIF,
             (unsigned) Ntf_STATUS_BIT_EMAIL,
@@ -1320,7 +1320,7 @@ void Ntf_SendPendingNotifByEMailToAllUsrs (void)
 
    /***** Delete old notifications ******/
    sprintf (Query,"DELETE LOW_PRIORITY FROM notif"
-	          " WHERE UNIX_TIMESTAMP(TimeNotif) < UNIX_TIMESTAMP()-%lu",
+                  " WHERE TimeNotif<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_OLD_NOTIF);
    DB_QueryDELETE (Query,"can not remove old notifications");
   }
@@ -1877,7 +1877,7 @@ static unsigned Ntf_GetNumberOfMyNewUnseenNtfs (void)
    /***** Get number of places with a name from database *****/
    sprintf (Query,"SELECT COUNT(*) FROM notif"
                   " WHERE ToUsrCod='%ld' AND (Status & %u)=0"
-                  " AND UNIX_TIMESTAMP(TimeNotif)>'%ld'",
+                  " AND TimeNotif>FROM_UNIXTIME('%ld')",
             Gbl.Usrs.Me.UsrDat.UsrCod,
             (unsigned) (Ntf_STATUS_BIT_READ | Ntf_STATUS_BIT_REMOVED),
             Gbl.Usrs.Me.UsrLast.LastAccNotif);
diff --git a/swad_password.c b/swad_password.c
index 64aca8546..74bd9caaa 100644
--- a/swad_password.c
+++ b/swad_password.c
@@ -456,7 +456,7 @@ void Pwd_SetMyPendingPassword (char PlainPassword[Pwd_MAX_LENGTH_PLAIN_PASSWORD+
 
    /***** Remove expired pending passwords from database *****/
    sprintf (Query,"DELETE FROM pending_passwd"
-                  " WHERE (UNIX_TIMESTAMP() > UNIX_TIMESTAMP(DateAndTime)+'%ld')",
+                  " WHERE DateAndTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_OLD_PENDING_PASSWORDS);
    DB_QueryDELETE (Query,"can not remove expired pending passwords");
 
diff --git a/swad_photo.c b/swad_photo.c
index ecad56486..2f136e840 100644
--- a/swad_photo.c
+++ b/swad_photo.c
@@ -1237,7 +1237,7 @@ static long Pho_GetDegWithAvgPhotoLeastRecentlyUpdated (void)
       /***** 2. If all the degrees are in table, choose the least recently updated *****/
       /* Get degrees from database */
       sprintf (Query,"SELECT DegCod FROM sta_degrees"
-	             " WHERE UNIX_TIMESTAMP(TimeAvgPhoto)<UNIX_TIMESTAMP()-%ld"
+                     " WHERE TimeAvgPhoto<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')"
 	             " ORDER BY TimeAvgPhoto LIMIT 1",
                Cfg_MIN_TIME_TO_RECOMPUTE_AVG_PHOTO);
       NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get degrees");
@@ -1287,7 +1287,8 @@ static long Pho_GetTimeAvgPhotoWasComputed (long DegCod)
 
    /***** Get last time an average photo was computed from database *****/
    sprintf (Query,"SELECT MIN(UNIX_TIMESTAMP(TimeAvgPhoto))"
-                  " FROM sta_degrees WHERE DegCod='%ld'",DegCod);
+                  " FROM sta_degrees WHERE DegCod='%ld'",
+            DegCod);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get last time an average photo was computed");
 
    if (NumRows == 1)
diff --git a/swad_preference.c b/swad_preference.c
index e65b37acc..380dd9851 100644
--- a/swad_preference.c
+++ b/swad_preference.c
@@ -213,7 +213,7 @@ void Pre_RemoveOldPrefsFromIP (void)
 
    /***** Remove old preferences *****/
    sprintf (Query,"DELETE LOW_PRIORITY FROM IP_prefs"
-                  " WHERE UNIX_TIMESTAMP() > UNIX_TIMESTAMP(LastChange)+%ld",
+                  " WHERE LastChange<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_IP_PREFS);
    DB_QueryDELETE (Query,"can not remove old preferences");
   }
diff --git a/swad_profile.c b/swad_profile.c
index 1b8a882fa..540a6e4fd 100644
--- a/swad_profile.c
+++ b/swad_profile.c
@@ -717,13 +717,13 @@ static unsigned long Prf_GetRankingNumClicksPerDay (long UsrCod)
                   " AS NumClicksPerDay"
                   " FROM usr_figures"
                   " WHERE UsrCod<>'%ld'"	// Necessary because the following comparison is not exact in floating point
-                  " AND NumClicks>='0' AND UNIX_TIMESTAMP(FirstClickTime)>'0')"
+                  " AND NumClicks>='0' AND FirstClickTime>FROM_UNIXTIME('0'))"
                   " AS TableNumClicksPerDay"
                   " WHERE NumClicksPerDay>"
                   "(SELECT NumClicks/(DATEDIFF(NOW(),FirstClickTime)+1)"
                   " FROM usr_figures"
                   " WHERE UsrCod='%ld'"
-                  " AND NumClicks>='0' AND UNIX_TIMESTAMP(FirstClickTime)>'0')",
+                  " AND NumClicks>='0' AND FirstClickTime>FROM_UNIXTIME('0'))",
 	    UsrCod,UsrCod);
    return DB_QueryCOUNT (Query,"can not get ranking using number of clicks per day");
   }
@@ -738,7 +738,7 @@ static unsigned long Prf_GetNumUsrsWithNumClicksPerDay (void)
 
    /***** Select number of rows with values already calculated *****/
    sprintf (Query,"SELECT COUNT(*) FROM usr_figures"
-	          " WHERE NumClicks>='0' AND UNIX_TIMESTAMP(FirstClickTime)>'0'");
+	          " WHERE NumClicks>='0' AND FirstClickTime>FROM_UNIXTIME('0')");
    return DB_QueryCOUNT (Query,"can not get number of users with number of clicks per day");
   }
 
diff --git a/swad_session.c b/swad_session.c
index 907a8afbe..549043d20 100644
--- a/swad_session.c
+++ b/swad_session.c
@@ -236,9 +236,11 @@ void Ses_RemoveExpiredSessions (void)
    /* A session expire when last click (LastTime) is too old,
       or when there was at least one refresh (navigator supports AJAX) and last refresh is too old (browser probably was closed) */
    sprintf (Query,"DELETE LOW_PRIORITY FROM sessions WHERE"
-                  " (UNIX_TIMESTAMP() > UNIX_TIMESTAMP(LastTime)+%ld) OR"
-                  " ((UNIX_TIMESTAMP(LastRefresh) > UNIX_TIMESTAMP(LastTime)+1) AND"
-                  " (UNIX_TIMESTAMP() > UNIX_TIMESTAMP(LastRefresh)+%ld))",
+                  " LastTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu') OR"
+                  " LastRefresh BETWEEN "
+                  "(LastTime+INTERVAL 1 SECOND)"
+                  " AND "
+                  "FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_CLOSE_SESSION_FROM_LAST_CLICK,
             Cfg_TIME_TO_CLOSE_SESSION_FROM_LAST_REFRESH);
    DB_QueryDELETE (Query,"can not remove expired sessions");
diff --git a/swad_statistic.c b/swad_statistic.c
index ddeeafa52..491a13a73 100644
--- a/swad_statistic.c
+++ b/swad_statistic.c
@@ -235,70 +235,6 @@ void Sta_GetRemoteAddr (void)
       Gbl.IP[0] = '\0';
   }
 
-/*****************************************************************************/
-/********* If this click is made from the same IP too fast, abort ************/
-/*****************************************************************************/
-/*
-void Sta_ExitIfTooFast (void)
-  {
-   extern const char *Txt_STR_LANG_ID[Txt_NUM_LANGUAGES];
-   extern const char *Txt_Too_fast;
-   extern const char *Txt_Go_back;
-   char Query[512];
-   unsigned NumClicks;	// Very recent clicks from this IP (0 or 1)
-
-   ***** Some actions can be made fast *****
-   if (Gbl.CurrentAct == ActRefCon    ||	// Refresh connected
-       Gbl.CurrentAct == ActRefLstClk ||	// Refresh last clicks
-       Gbl.CurrentAct == ActAutUsrChgLan)	// Change my language automatically just after log in
-      return;
-
-   ***** Get if a click/refresh is made from the same IP very recently *****
-   sprintf (Query,"SELECT COUNT(*) FROM IP_last"
-                  " WHERE IP='%s' AND UNIX_TIMESTAMP(LastClick)>UNIX_TIMESTAMP()-%u",
-            Gbl.IP,Cfg_MIN_TIME_BETWEEN_2_CLICKS_FROM_THE_SAME_IP);
-   NumClicks = (unsigned) DB_QueryCOUNT (Query,"can not get the number of very recent clicks");
-
-   ***** Remove old clicks/refreshes *****
-   sprintf (Query,"DELETE FROM IP_last"
-                  " WHERE UNIX_TIMESTAMP(LastClick)<=UNIX_TIMESTAMP()-%u",
-                  Cfg_MIN_TIME_BETWEEN_2_CLICKS_FROM_THE_SAME_IP);
-   DB_QueryDELETE (Query,"can not remove old last IP");
-
-   ***** Replace last click/refresh from this IP *****
-   sprintf (Query,"REPLACE INTO IP_last"
-                  " (IP,LastClick)"
-                  " VALUES ('%s',NOW())",
-	    Gbl.IP);
-   DB_QueryREPLACE (Query,"can not update last IP");
-
-   ***** If too fast, write warning and exit *****
-   if (NumClicks)	// Too fast
-     {
-      ***** Write header to standard output to avoid timeout *****
-      // Two \r\n are necessary
-      fprintf (stdout,"Content-type: text/html; charset=windows-1252\r\n\r\n"
-                      "<!DOCTYPE html>\n"
-                      "<html lang=\"%s\">\n"
-		      "<head>"
-		      "<title>%s</title>"
-		      "</head>"
-		      "<body>"
-		      "<h1 style=\"text-align:center;\">%s</h1>"
-		      "<h2 style=\"text-align:center;\">"
-		      "<a href=\"\" onclick=\"window.history.back();\">&larr; %s</a>"
-		      "</h2>"
-		      "</body>"
-		      "</html>",
-	       Txt_STR_LANG_ID[Gbl.Prefs.Language],
-	       Cfg_PLATFORM_FULL_NAME,
-	       Txt_Too_fast,
-	       Txt_Go_back);
-      exit (0);
-      // sleep (Cfg_MIN_TIME_BETWEEN_2_CLICKS_FROM_THE_SAME_IP);	// Sleep those seconds
-     }
-  }
-*/
 /*****************************************************************************/
 /**************************** Log access in database *************************/
 /*****************************************************************************/
@@ -412,7 +348,7 @@ void Sta_RemoveOldEntriesRecentLog (void)
 
    /***** Remove all expired clipboards *****/
    sprintf (Query,"DELETE LOW_PRIORITY FROM log_recent"
-                  " WHERE UNIX_TIMESTAMP(ClickTime)<UNIX_TIMESTAMP()-%ld",
+                  " WHERE ClickTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Sta_SECONDS_IN_RECENT_LOG);
    DB_QueryDELETE (Query,"can not remove old entries from recent log");
   }
@@ -1118,12 +1054,11 @@ static void Sta_ShowHits (Sta_GlobalOrCourseAccesses_t GlobalOrCourse)
                   StrQueryCountType,LogTable);
 	 break;
      }
-   sprintf (QueryAux," WHERE"
-	             " UNIX_TIMESTAMP(%s.ClickTime)>='%ld'"
-	             " AND"
-	             " UNIX_TIMESTAMP(%s.ClickTime)<='%ld'",
-            LogTable,(long) Gbl.DateRange.TimeUTC[0],
-            LogTable,(long) Gbl.DateRange.TimeUTC[1]);
+   sprintf (QueryAux," WHERE %s.ClickTime"
+	             " BETWEEN FROM_UNIXTIME('%ld') AND FROM_UNIXTIME('%ld')",
+            LogTable,
+            (long) Gbl.DateRange.TimeUTC[0],
+            (long) Gbl.DateRange.TimeUTC[1]);
    strcat (Query,QueryAux);
 
    switch (GlobalOrCourse)
@@ -2168,12 +2103,12 @@ static void Sta_ShowDistrAccessesPerDaysAndHour (unsigned long NumRows,MYSQL_RES
       if (NumRow == 1)
          Dat_AssignDate (&PreviousReadDate,&CurrentReadDate);
 
-      /* Update number of pages generated per hour */
+      /* Update number of hits per hour */
       if (PreviousReadDate.Year  != CurrentReadDate.Year  ||
           PreviousReadDate.Month != CurrentReadDate.Month ||
           PreviousReadDate.Day   != CurrentReadDate.Day)	// Current read date (CurrentReadDate) is older than previous read date (PreviousReadDate) */
         {
-         /* In the next loop we show (NumDaysFromLastDateToCurrDate-1) days (the menos antiguos) with 0 clicks
+         /* In the next loop we show (NumDaysFromLastDateToCurrDate-1) days with 0 clicks
             and a last day (older) with Hits.Num */
          Dat_AssignDate (&Date,&LastDate);
          NumDaysFromLastDateToCurrDate = Dat_GetNumDaysBetweenDates (&PreviousReadDate,&LastDate);
diff --git a/swad_statistic.h b/swad_statistic.h
index 1ade0f7a3..e4982fcfe 100644
--- a/swad_statistic.h
+++ b/swad_statistic.h
@@ -138,7 +138,6 @@ typedef enum
 /*****************************************************************************/
 
 void Sta_GetRemoteAddr (void);
-void Sta_ExitIfTooFast (void);
 void Sta_LogAccess (const char *Comments);
 void Sta_RemoveOldEntriesRecentLog (void);
 void Sta_AskShowCrsHits (void);
diff --git a/swad_test.c b/swad_test.c
index 439e8640b..943db5ece 100644
--- a/swad_test.c
+++ b/swad_test.c
@@ -561,13 +561,13 @@ static void Tst_ShowTstTotalMark (double TotalScore)
 
 static bool Tst_CheckIfNextTstAllowed (void)
   {
-   extern const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y;
-   extern const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y_on_DATE_Z;
+   extern const char *Txt_Test;
+   extern const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until;
    char Query[512];
    MYSQL_RES *mysql_res;
    MYSQL_ROW row;
    long NumSecondsFromNowToNextAccTst = -1L;	// Access allowed when this number <= 0
-   unsigned Year,Month,Day,Hour,Minute,Second;
+   time_t TimeNextTestUTC = (time_t) 0;
 
    /***** Superusers are allowed to do all test they want *****/
    if (Gbl.Usrs.Me.LoggedRole == Rol_SYS_ADM)
@@ -575,7 +575,7 @@ static bool Tst_CheckIfNextTstAllowed (void)
 
    /***** Get date of next allowed access to test from database *****/
    sprintf (Query,"SELECT UNIX_TIMESTAMP(LastAccTst+INTERVAL (NumQstsLastTst*%lu) SECOND)-UNIX_TIMESTAMP(),"
-	          "LastAccTst+INTERVAL (NumQstsLastTst*%lu) SECOND"
+	          "UNIX_TIMESTAMP(LastAccTst+INTERVAL (NumQstsLastTst*%lu) SECOND)"
                   " FROM crs_usr"
                   " WHERE CrsCod='%ld' AND UsrCod='%ld'",
             Gbl.Test.Config.MinTimeNxtTstPerQst,
@@ -587,9 +587,8 @@ static bool Tst_CheckIfNextTstAllowed (void)
       row = mysql_fetch_row (mysql_res);
       if (row[0])
          if (sscanf (row[0],"%ld",&NumSecondsFromNowToNextAccTst) == 1)
-            /* Datetime of next access allowed (row[1]) */
-            if (sscanf (row[1],"%04u-%02u-%02u %02u:%02u:%02u",&Year,&Month,&Day,&Hour,&Minute,&Second) != 6)
-               Lay_ShowErrorAndExit ("Wrong date of next allowed access to test.");
+            /* Time UTC of next access allowed (row[1]) */
+            TimeNextTestUTC = Dat_GetUNIXTimeFromStr (row[1]);
      }
    else
       Lay_ShowErrorAndExit ("Error when reading date of next allowed access to test.");
@@ -600,15 +599,31 @@ static bool Tst_CheckIfNextTstAllowed (void)
    /***** Check if access is allowed *****/
    if (NumSecondsFromNowToNextAccTst > 0)
      {
-      if (Year  == Gbl.Now.Date.Year &&
-          Month == Gbl.Now.Date.Month &&
-          Day   == Gbl.Now.Date.Day)		// Next access allowed is today
-         sprintf (Gbl.Message,Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y,
-                  Gbl.CurrentCrs.Crs.FullName,Hour,Minute,Second);
-      else
-         sprintf (Gbl.Message,Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y_on_DATE_Z,
-                  Gbl.CurrentCrs.Crs.FullName,Hour,Minute,Second,Year,Month,Day);
-      Lay_ShowAlert (Lay_WARNING,Gbl.Message);
+      /***** Start frame *****/
+      Lay_StartRoundFrameTable (NULL,2,Txt_Test);
+      Lay_WriteHeaderClassPhoto (1,false,false,
+				 Gbl.CurrentIns.Ins.InsCod,
+				 Gbl.CurrentDeg.Deg.DegCod,
+				 Gbl.CurrentCrs.Crs.CrsCod);
+
+      /***** Write warning *****/
+      fprintf (Gbl.F.Out,"<tr>"
+	                 "<td class=\"DAT CENTER_MIDDLE\">");
+      fprintf (Gbl.F.Out,Txt_You_can_not_make_a_new_test_in_the_course_X_until,
+               Gbl.CurrentCrs.Crs.FullName);
+      fprintf (Gbl.F.Out,": "
+	                 "<span id=\"date_next_test\">"
+	                 "</span>"
+                         "<script type=\"text/javascript\">"
+			 "writeLocalDateTimeFromUTC('date_next_test',%ld,'&nbsp;');"
+			 "</script>"
+			 "</td>"
+			 "</tr>",
+	       (long) TimeNextTestUTC);
+
+      /***** End frame *****/
+      Lay_EndRoundFrameTable ();
+
       return false;
      }
    return true;
@@ -6209,8 +6224,8 @@ static void Tst_ShowResultsOfTestExams (struct UsrData *UsrDat)
 	          "NumQsts,NumQstsNotBlank,Score"
 	          " FROM tst_exams"
                   " WHERE CrsCod='%ld' AND UsrCod='%ld'"
-                  " AND UNIX_TIMESTAMP(TstTime)>='%ld'"
-                  " AND UNIX_TIMESTAMP(TstTime)<='%ld'"
+                  " AND TstTime>=FROM_UNIXTIME('%ld')"
+                  " AND TstTime<=FROM_UNIXTIME('%ld')"
                   " ORDER BY TstCod",
             Gbl.CurrentCrs.Crs.CrsCod,
             UsrDat->UsrCod,
diff --git a/swad_text.c b/swad_text.c
index b33dd1a6f..03a6ab537 100644
--- a/swad_text.c
+++ b/swad_text.c
@@ -49860,64 +49860,25 @@ const char *Txt_You_can_not_leave_the_web_address_empty =
 	"You can not leave the web address empty.";		// Necessita de tradução
 #endif
 
-const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y =	// Warning: it is very important to include %s and three %02u in the following sentences
+const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until =	// Warning: it is very important to include %s in the following sentences
 #if   L==0
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02uh%02u'%02u&quot;";		// Necessita traduccio
+	"No puede hacer un nuevo test en la asignatura <strong>%s</strong> hasta";	// Necessita traduccio
 #elif L==1
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02uh%02u'%02u&quot;";			// Need Übersetzung
+	"You can not make a new test in the course <strong>%s</strong> until";		// Need Übersetzung
 #elif L==2
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02uh%02u'%02u&quot;";
+	"You can not make a new test in the course <strong>%s</strong> until";
 #elif L==3
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02uh%02u'%02u&quot;";
+	"No puede hacer un nuevo test en la asignatura <strong>%s</strong> hasta";
 #elif L==4
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02uh%02u'%02u&quot;";			// Besoin de traduction
+	"You can not make a new test in the course <strong>%s</strong> until";		// Besoin de traduction
 #elif L==5
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02uh%02u'%02u&quot;";		// Okoteve traducción
+	"No puede hacer un nuevo test en la asignatura <strong>%s</strong> hasta";	// Okoteve traducción
 #elif L==6
-	"Non puoi fare un nuovo test nel corso <strong>%s</strong>"
-	" fino al %02uh%02u'%02u&quot;";
+	"Non puoi fare un nuovo test nel corso <strong>%s</strong> fino";
 #elif L==7
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02uh%02u'%02u&quot;";			// Potrzebujesz tlumaczenie
+	"You can not make a new test in the course <strong>%s</strong> until";		// Potrzebujesz tlumaczenie
 #elif L==8
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02uh%02u'%02u&quot;";			// Necessita de tradução
-#endif
-
-const char *Txt_You_can_not_make_a_new_test_in_the_course_X_until_TIME_Y_on_DATE_Z =	// Warning: it is very important to include %s, five %02u and %04u in the following sentences
-#if   L==0
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02u:%02u:%02u del %04u-%02u-%02u";		// Necessita traduccio
-#elif L==1
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02u:%02u:%02u on %04u-%02u-%02u";		// Need Übersetzung
-#elif L==2
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02u:%02u:%02u on %04u-%02u-%02u";
-#elif L==3
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02u:%02u:%02u del %04u-%02u-%02u";
-#elif L==4
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02u:%02u:%02u on %04u-%02u-%02u";		// Besoin de traduction
-#elif L==5
-	"No puede hacer un nuevo test en la asignatura <strong>%s</strong>"
-	" hasta las %02u:%02u:%02u del %04u-%02u-%02u";		// Okoteve traducción
-#elif L==6
-	"Non puoi fare un nuovo test nel corso <strong>%s</strong>"
-	" fino al %02u:%02u:%02u del %04u-%02u-%02u";
-#elif L==7
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02u:%02u:%02u on %04u-%02u-%02u";		// Potrzebujesz tlumaczenie
-#elif L==8
-	"You can not make a new test in the course <strong>%s</strong>"
-	" until %02u:%02u:%02u on %04u-%02u-%02u";		// Necessita de tradução
+	"You can not make a new test in the course <strong>%s</strong> until";		// Necessita de tradução
 #endif
 
 const char *Txt_You_can_not_paste_file_or_folder_here =
diff --git a/swad_web_service.c b/swad_web_service.c
index b7cd0c5da..fbed2c8f6 100644
--- a/swad_web_service.c
+++ b/swad_web_service.c
@@ -474,7 +474,7 @@ static int Svc_RemoveOldWSKeys (void)
    /* A session expire when last click (LastTime) is too old,
       or when there was at least one refresh (navigator supports AJAX) and last refresh is too old (browser probably was closed) */
    sprintf (Query,"DELETE LOW_PRIORITY FROM ws_keys WHERE"
-                  " UNIX_TIMESTAMP() > UNIX_TIMESTAMP(LastTime)+%ld",
+                  " LastTime<FROM_UNIXTIME(UNIX_TIMESTAMP()-'%lu')",
             Cfg_TIME_TO_DELETE_Svc_KEY);
    if (mysql_query (&Gbl.mysql,Query))
       return soap_receiver_fault (Gbl.soap,
@@ -2545,7 +2545,8 @@ int swad__getNotifications (struct soap *soap,
    /***** Get my notifications from database *****/
    sprintf (Query,"SELECT NtfCod,NotifyEvent,UNIX_TIMESTAMP(TimeNotif),"
 	          "FromUsrCod,InsCod,CtrCod,DegCod,CrsCod,Cod,Status"
-                  " FROM notif WHERE ToUsrCod=%ld AND UNIX_TIMESTAMP(TimeNotif)>=%ld"
+                  " FROM notif"
+                  " WHERE ToUsrCod='%ld' AND TimeNotif>=FROM_UNIXTIME('%ld')"
                   " ORDER BY TimeNotif DESC",
             Gbl.Usrs.Me.UsrDat.UsrCod,beginTime);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get user's notifications");
@@ -3413,11 +3414,16 @@ static int Svc_GetTstQuestions (long CrsCod,long BeginTime,struct swad__getTests
 		  " AND tst_questions.QstCod=tst_question_tags.QstCod"
 		  " AND tst_question_tags.TagCod=tst_tags.TagCod"
 		  " AND tst_tags.CrsCod='%ld'"
-		  " AND (UNIX_TIMESTAMP(tst_questions.EditTime)>='%ld'"
-                  " OR UNIX_TIMESTAMP(tst_tags.ChangeTime)>='%ld')"
+		  " AND "
+		  "("
+		  "tst_questions.EditTime>=FROM_UNIXTIME('%ld')"
+                  " OR "
+                  "tst_tags.ChangeTime>=FROM_UNIXTIME('%ld')"
+                  ")"
                   " ORDER BY QstCod",
             CrsCod,CrsCod,CrsCod,
-            BeginTime,BeginTime);
+            BeginTime,
+            BeginTime);
    NumRows = (unsigned) DB_QuerySELECT (Query,&mysql_res,"can not get test questions");
 
    getTestsOut->questionsArray.__size = (int) NumRows;
@@ -3492,11 +3498,17 @@ static int Svc_GetTstAnswers (long CrsCod,long BeginTime,struct swad__getTestsOu
 		  " AND tst_questions.QstCod=tst_question_tags.QstCod"
 		  " AND tst_question_tags.TagCod=tst_tags.TagCod"
 		  " AND tst_tags.CrsCod='%ld'"
-		  " AND (UNIX_TIMESTAMP(tst_questions.EditTime)>='%ld'"
-                  " OR UNIX_TIMESTAMP(tst_tags.ChangeTime)>='%ld'))"
+		  " AND "
+		  "("
+		  "tst_questions.EditTime>=FROM_UNIXTIME('%ld')"
+                  " OR "
+                  "tst_tags.ChangeTime>=FROM_UNIXTIME('%ld')"
+                  ")"
+                  ")"
                   " ORDER BY QstCod,AnsInd",
             CrsCod,CrsCod,CrsCod,
-            BeginTime,BeginTime);
+            BeginTime,
+            BeginTime);
    NumRows = (unsigned) DB_QuerySELECT (Query,&mysql_res,"can not get test answers");
 
    getTestsOut->answersArray.__size = (int) NumRows;
@@ -3571,11 +3583,17 @@ static int Svc_GetTstQuestionTags (long CrsCod,long BeginTime,struct swad__getTe
 		  " AND tst_questions.QstCod=tst_question_tags.QstCod"
 		  " AND tst_question_tags.TagCod=tst_tags.TagCod"
 		  " AND tst_tags.CrsCod='%ld'"
-		  " AND (UNIX_TIMESTAMP(tst_questions.EditTime)>='%ld'"
-                  " OR UNIX_TIMESTAMP(tst_tags.ChangeTime)>='%ld'))"
+		  " AND "
+		  "("
+		  "tst_questions.EditTime>=FROM_UNIXTIME('%ld')"
+                  " OR "
+                  "tst_tags.ChangeTime>=FROM_UNIXTIME('%ld')"
+                  ")"
+                  ")"
                   " ORDER BY QstCod,TagInd",
             CrsCod,CrsCod,CrsCod,
-            BeginTime,BeginTime);
+            BeginTime,
+            BeginTime);
    NumRows = (unsigned) DB_QuerySELECT (Query,&mysql_res,"can not get test question tags");
 
    getTestsOut->questionTagsArray.__size = (int) NumRows;