diff --git a/js/swad.js b/js/swad.js
index 4862d8740..cda4f786f 100644
--- a/js/swad.js
+++ b/js/swad.js
@@ -24,7 +24,7 @@
 // Global variable used in refreshConnected()
 var ActionAJAX;
 
-// Global variables used in writeLocalTime()
+// Global variables used in writeLocalClock()
 var secondsSince1970UTC;
 
 // Global variables used in writeClockConnected()
@@ -88,93 +88,166 @@ function writeLocalDateTimeFromUTC(id,secsSince1970UTC,separator) {
 
 // Set local date-time form fields from UTC time
 function setLocalDateTimeFormFromUTC(id,secsSince1970UTC) {
-	var d = new Date;
-	var YearForm = document.getElementById(id+'Year');
+	var FormYea = document.getElementById(id+'Year');
+	var FormMon = document.getElementById(id+'Month');
+	var FormDay = document.getElementById(id+'Day');
+	var FormHou = document.getElementById(id+'Hour');
+	var FormMin = document.getElementById(id+'Minute');
+	var FormSec = document.getElementById(id+'Second');
+	var d;
 	var Year;
+	var YearIsValid = false;
 
-	d.setTime(secsSince1970UTC * 1000);
+	if (secsSince1970UTC) {
+		d = new Date;
+		d.setTime(secsSince1970UTC * 1000);
+		Year = d.getFullYear();
+		for (var i=0; i<FormYea.options.length && !YearIsValid; i++)
+			if (FormYea.options[i].value == Year) {
+				FormYea.options[i].selected = true;
+				YearIsValid = true;
+			}
+		FormMon.disabled = false;
+		FormDay.disabled = false;
+		FormHou.disabled = false;
+		FormMin.disabled = false;
+		FormSec.disabled = false;
+		FormMon.options[d.getMonth()+1].selected = true;
+		FormDay.options[d.getDate()   ].selected = true;
+		FormHou.options[d.getHours()  ].selected = true;
+		FormMin.options[d.getMinutes()].selected = true;
+		FormSec.options[d.getSeconds()].selected = true;
+	}
+	
+	if (!YearIsValid) {
+		FormYea.options[0].selected = true;
+		FormMon.options[0].selected = true;
+		FormDay.options[0].selected = true;
+		FormHou.options[0].selected = true;
+		FormMin.options[0].selected = true;
+		FormSec.options[0].selected = true;
 
-	Year = d.getFullYear()
-	for (var i=0; i<YearForm.options.length ; i++)
-		if (YearForm.options[i].value == Year) {
-			YearForm.options[i].selected = true;
-			break;
-		}
-	document.getElementById(id+'Month' ).options[d.getMonth()+1].selected = true;
-	document.getElementById(id+'Day'   ).options[d.getDate()   ].selected = true;
-	document.getElementById(id+'Hour'  ).options[d.getHours()  ].selected = true;
-	document.getElementById(id+'Minute').options[d.getMinutes()].selected = true;
-	document.getElementById(id+'Second').options[d.getSeconds()].selected = true;
+		FormMon.disabled = true;
+		FormDay.disabled = true;
+		FormHou.disabled = true;
+		FormMin.disabled = true;
+		FormSec.disabled = true;
+	}
 }
 
 // Set UTC time from local date-time form fields 
 function setUTCFromLocalDateTimeForm(id) {
-	var d = new Date;
-	var Year  = document.getElementById(id+'Year'  ).value;
-	var Month = document.getElementById(id+'Month' ).value;
-	var Day   = document.getElementById(id+'Day'   ).value;
+	var FormYea = document.getElementById(id+'Year');
+	var FormMon = document.getElementById(id+'Month');
+	var FormDay = document.getElementById(id+'Day');
+	var FormHou = document.getElementById(id+'Hour');
+	var FormMin = document.getElementById(id+'Minute');
+	var FormSec = document.getElementById(id+'Second');
+	var FormTimeUTC = document.getElementById(id+'TimeUTC');
+	var d;
+	var Yea = FormYea.value;
+	var Mon;
+	var Day;
 	
-	if (Year == 0 || Month == 0 || Day == 0)
-		document.getElementById(id+'TimeUTC').value = 0;
-        else {
+	if (Yea == 0) {
+		FormYea.options[0].selected = true;
+		FormMon.options[0].selected = true;
+		FormDay.options[0].selected = true;
+		FormHou.options[0].selected = true;
+		FormMin.options[0].selected = true;
+		FormSec.options[0].selected = true;
+
+		FormMon.disabled = true;
+		FormDay.disabled = true;
+		FormHou.disabled = true;
+		FormMin.disabled = true;
+		FormSec.disabled = true;
+
+		FormTimeUTC.value = 0;
+	}
+	else {
+		FormMon.disabled = false;
+		FormDay.disabled = false;
+		FormHou.disabled = false;
+		FormMin.disabled = false;
+		FormSec.disabled = false;
+
+		Mon = FormMon.value;
+		if (Mon == 0)
+			Mon = 1;
+		Day = FormDay.value;
+		if (Day == 0)
+			Day = 1;
+
 		// Important: set year first in order to work properly with leap years
-		d.setFullYear(Year);
-		d.setMonth   (Month-1);
+		d = new (Date);
+		d.setFullYear(Yea);
+		d.setMonth   (Mon-1);
 		d.setDate    (Day);
-		d.setHours   (document.getElementById(id+'Hour'  ).value);
-		d.setMinutes (document.getElementById(id+'Minute').value);
-		d.setSeconds (document.getElementById(id+'Second').value);
+		d.setHours   (FormHou.value);
+		d.setMinutes (FormMin.value);
+		d.setSeconds (FormSec.value);
 		d.setMilliseconds(0);
 	
-		document.getElementById(id+'TimeUTC').value = d.getTime() / 1000;
+		FormTimeUTC.value = d.getTime() / 1000;
 	}
 }
 
 // Adjust a date form correcting days in the month
 function adjustDateForm (id) {
-	var Days = 31;
-	var YearForm  = document.getElementById(id+'Year' );
-	var MonthForm = document.getElementById(id+'Month');
-	var DayForm   = document.getElementById(id+'Day'  );
-	var Year = YearForm.options[YearForm.selectedIndex].value;
+	var FormYea = document.getElementById(id+'Year' );
+	var FormMon = document.getElementById(id+'Month');
+	var FormDay = document.getElementById(id+'Day'  );
+	var Yea = FormYea.options[FormYea.selectedIndex].value;
+	var Days;
 
-	if (MonthForm.options[2].selected)			// Adjust days of february
-		Days = ((((Year % 4) == 0) && ((Year % 100) != 0)) || ((Year % 400) == 0)) ? 29 : 28;
-	else if (MonthForm.options[ 4].selected ||
-		 MonthForm.options[ 6].selected ||
-		 MonthForm.options[ 9].selected ||
-		 MonthForm.options[11].selected)
-		Days = 30;
-
-	if (DayForm.selectedIndex > Days)
-		DayForm.options[Days].selected = true;
-
-	for (var i=DayForm.options.length; i<=Days ; i++) {	// Create new days
-		var x = String (i);
-		DayForm.options[i] = new Option(x,x);
+	if (FormYea.selectedIndex > 0) {
+		if (FormMon.options[0].selected) {			// No month selected, set to january
+			FormMon.options[1].selected = true;
+			Days = 31;
+		}
+		else if (FormMon.options[2].selected)			// Adjust days of february
+			Days = ((((Yea % 4) == 0) && ((Yea % 100) != 0)) || ((Yea % 400) == 0)) ? 29 : 28;
+		else if (FormMon.options[ 4].selected ||
+			 FormMon.options[ 6].selected ||
+			 FormMon.options[ 9].selected ||
+			 FormMon.options[11].selected)
+			Days = 30;
+		else
+			Days = 31;
+	
+		if (FormDay.options[0].selected)			// No day selected, set to 1
+			FormDay.options[1].selected = true;
+		else if (FormDay.selectedIndex > Days)
+			FormDay.options[Days].selected = true;
+	
+		for (var i=FormDay.options.length; i<=Days ; i++) {	// Create new days
+			var x = String (i);
+			FormDay.options[i] = new Option(x,x);
+		}
+		for (var i=FormDay.options.length-1; i>Days; i--)	// Remove days
+			FormDay.options[i] = null;
 	}
-	for (var i=DayForm.options.length-1; i>Days; i--)	// Remove days
-		DayForm.options[i] = null;
 }
 
 // Set a the date in a date form to a specified date  
-function setDateTo (Day,Month,Year) {
-	document.getElementById('StartYear'  ).options[Year ].selected = true;
-	document.getElementById('StartMonth' ).options[Month].selected = true;
+function setDateTo (Day,Mon,Yea) {
+	document.getElementById('StartYear'  ).options[Yea].selected = true;
+	document.getElementById('StartMonth' ).options[Mon].selected = true;
 	adjustDateForm ('Start')
-	document.getElementById('StartDay'   ).options[Day  ].selected = true;
-	document.getElementById('StartHour'  ).options[0    ].selected = true;
-	document.getElementById('StartMinute').options[0    ].selected = true;
-	document.getElementById('StartSecond').options[0    ].selected = true;
+	document.getElementById('StartDay'   ).options[Day].selected = true;
+	document.getElementById('StartHour'  ).options[0  ].selected = true;
+	document.getElementById('StartMinute').options[0  ].selected = true;
+	document.getElementById('StartSecond').options[0  ].selected = true;
 	setUTCFromLocalDateTimeForm('Start');
 
-	document.getElementById('EndYear'    ).options[Year ].selected = true;
-	document.getElementById('EndMonth'   ).options[Month].selected = true;
+	document.getElementById('EndYear'    ).options[Yea].selected = true;
+	document.getElementById('EndMonth'   ).options[Mon].selected = true;
 	adjustDateForm ('End')
-	document.getElementById('EndDay'     ).options[Day  ].selected = true;
-	document.getElementById('EndHour'    ).options[23   ].selected = true;
-	document.getElementById('EndMinute'  ).options[59   ].selected = true;
-	document.getElementById('EndSecond'  ).options[59   ].selected = true;
+	document.getElementById('EndDay'     ).options[Day].selected = true;
+	document.getElementById('EndHour'    ).options[23 ].selected = true;
+	document.getElementById('EndMinute'  ).options[59 ].selected = true;
+	document.getElementById('EndSecond'  ).options[59 ].selected = true;
 	setUTCFromLocalDateTimeForm('End');
 }
 
@@ -186,7 +259,7 @@ function writeLocalClock() {
 	var StrH;
 	var StrM;
 
-	setTimeout('writeLocalTime()',60000);
+	setTimeout('writeLocalClock()',60000);
 
 	d.setTime(secondsSince1970UTC * 1000);
 	secondsSince1970UTC += 60;	// For next call
diff --git a/swad_changelog.h b/swad_changelog.h
index 8e0d9e6bf..f88617cf2 100644
--- a/swad_changelog.h
+++ b/swad_changelog.h
@@ -108,11 +108,13 @@
 /****************************** Public constants *****************************/
 /*****************************************************************************/
 
-#define Log_PLATFORM_VERSION	"SWAD 15.22.1 (2015/10/26)"
+#define Log_PLATFORM_VERSION	"SWAD 15.24 (2015/10/26)"
 
 // 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 15.24:    Oct 26, 2015	Lot of changes in swad.js related to date-times. (186336 lines)
+        Version 15.23:    Oct 26, 2015	Date-times to open groups are displayed in client local date-time. (186259 lines)
         Version 15.22.1:  Oct 26, 2015	Date-times in notices are displayed in client local date-time. (186344 lines)
         Version 15.22:    Oct 26, 2015	First click time in users' profiles is displayed in client local date-time. (186328 lines)
         Version 15.21.3:  Oct 26, 2015	Changes in date-times of test exams. (186325 lines)
diff --git a/swad_date.c b/swad_date.c
index fdb1bde86..bfe579739 100644
--- a/swad_date.c
+++ b/swad_date.c
@@ -63,11 +63,6 @@ const unsigned Dat_NumDaysMonth[1+12] =
 /***************************** Private prototypes ****************************/
 /*****************************************************************************/
 
-static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
-                                                         time_t TimeUTC,
-                                                         unsigned FirstYear,unsigned LastYear,
-                                                         bool SubmitFormOnChange,bool Disabled);
-
 /*****************************************************************************/
 /***************************** Get current time ******************************/
 /*****************************************************************************/
@@ -145,36 +140,6 @@ bool Dat_GetDateFromYYYYMMDD (struct Date *Date,const char *YYYYMMDD)
      }
   }
 
-/*****************************************************************************/
-/******* Get a struct DateTime from a string in YYYYMMDDHHMMSS format ********/
-/*****************************************************************************/
-
-bool Dat_GetDateTimeFromYYYYMMDDHHMMSS (struct DateTime *DateTime,const char *YYYYMMDDHHMMSS)
-  {
-   if (sscanf (YYYYMMDDHHMMSS,"%04u%02u%02u%02u%02u%02u",
-               &(DateTime->Date.Year),&(DateTime->Date.Month),&(DateTime->Date.Day),
-               &(DateTime->Time.Hour),&(DateTime->Time.Minute),&(DateTime->Time.Second)) == 6)
-     {
-      strncpy (DateTime->Date.YYYYMMDD,YYYYMMDDHHMMSS,4+2+2);
-      DateTime->YYYYMMDDHHMMSS[4+2+2] = '\0';
-
-      strncpy (DateTime->YYYYMMDDHHMMSS,YYYYMMDDHHMMSS,4+2+2+2+2+2);
-      DateTime->YYYYMMDDHHMMSS[4+2+2+2+2+2] = '\0';
-
-      return true;
-     }
-   else
-     {
-      DateTime->Date.Year = DateTime->Date.Month = DateTime->Date.Day = 0;
-      DateTime->Date.YYYYMMDD[0] = '\0';
-
-      DateTime->Time.Hour = DateTime->Time.Minute = DateTime->Time.Second = 0;
-      DateTime->YYYYMMDDHHMMSS[0] = '\0';
-
-      return false;
-     }
-  }
-
 /*****************************************************************************/
 /******************** Write div for client local time ************************/
 /*****************************************************************************/
@@ -241,6 +206,7 @@ void Dat_PutFormStartEndClientLocalDateTimesWithYesterdayToday (void)
             Txt_Start_date);
    /* Date-time */
    Dat_WriteFormClientLocalDateTimeFromTimeUTC ("Start",
+                                                "Start",
                                                 Gbl.DateRange.TimeUTC[0],
                                                 Cfg_LOG_START_YEAR,
 				                Gbl.Now.Date.Year,
@@ -274,6 +240,7 @@ void Dat_PutFormStartEndClientLocalDateTimesWithYesterdayToday (void)
             Txt_End_date);
    /* Date-time */
    Dat_WriteFormClientLocalDateTimeFromTimeUTC ("End",
+                                                "End",
                                                 Gbl.DateRange.TimeUTC[1],
                                                 Cfg_LOG_START_YEAR,
 				                Gbl.Now.Date.Year,
@@ -321,6 +288,7 @@ void Dat_PutFormStartEndClientLocalDateTimes (time_t TimeUTC[2])
 
       /* Date-time */
       Dat_WriteFormClientLocalDateTimeFromTimeUTC (Id[StartOrEndTime],
+                                                   Id[StartOrEndTime],
 	                                           TimeUTC[StartOrEndTime],
 	                                           Gbl.Now.Date.Year - 1,
 	                                           Gbl.Now.Date.Year + 1,
@@ -338,10 +306,11 @@ void Dat_PutFormStartEndClientLocalDateTimes (time_t TimeUTC[2])
 /************************* Show a form to enter a date ***********************/
 /*****************************************************************************/
 
-static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
-                                                         time_t TimeUTC,
-                                                         unsigned FirstYear,unsigned LastYear,
-                                                         bool SubmitFormOnChange,bool Disabled)
+void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
+                                                  const char *ParamName,
+                                                  time_t TimeUTC,
+                                                  unsigned FirstYear,unsigned LastYear,
+                                                  bool SubmitFormOnChange,bool Disabled)
   {
    extern const char *Txt_MONTHS_SMALL[12];
    unsigned Day;
@@ -356,12 +325,12 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
 	              "<tr>");
 
    /***** Year *****/
-   fprintf (Gbl.F.Out,"<td class=\"CENTER_MIDDLE\">"
+   fprintf (Gbl.F.Out,"<td class=\"RIGHT_MIDDLE\">"
                       "<select id=\"%sYear\" name=\"%sYear\""
                       " onchange=\""
                       "adjustDateForm('%s');"
                       "setUTCFromLocalDateTimeForm('%s');",
-	    Id,Id,Id,Id);
+	    Id,ParamName,Id,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
@@ -383,14 +352,14 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
                       " onchange=\""
                       "adjustDateForm('%s');"
                       "setUTCFromLocalDateTimeForm('%s');",
-	    Id,Id,Id,Id);
+	    Id,ParamName,Id,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
    fprintf (Gbl.F.Out,"\"");
    if (Disabled)
       fprintf (Gbl.F.Out," disabled=\"disabled\"");
-   fprintf (Gbl.F.Out,"><option value=\"0\">-</option>");
+   fprintf (Gbl.F.Out,"><option value=\"0\" disabled=\"disabled\">-</option>");
    for (Month = 1;
 	Month <= 12;
 	Month++)
@@ -400,10 +369,10 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
 	              "</td>");
 
    /***** Day *****/
-   fprintf (Gbl.F.Out,"<td class=\"CENTER_MIDDLE\">"
+   fprintf (Gbl.F.Out,"<td class=\"LEFT_MIDDLE\">"
 	              "<select id=\"%sDay\" name=\"%sDay\""
 	              " onchange=\"setUTCFromLocalDateTimeForm('%s');",
-            Id,Id,Id);
+            Id,ParamName,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
@@ -411,7 +380,7 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
    if (Disabled)
       fprintf (Gbl.F.Out," disabled=\"disabled\"");
    fprintf (Gbl.F.Out,">"
-	              "<option value=\"0\">-</option>");
+	              "<option value=\"0\" disabled=\"disabled\">-</option>");
    for (Day = 1;
 	Day <= 31;
 	Day++)
@@ -421,10 +390,10 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
 	              "</td>");
 
    /***** Hour *****/
-   fprintf (Gbl.F.Out,"<td class=\"DAT LEFT_MIDDLE\">,&nbsp;"
+   fprintf (Gbl.F.Out,"<td class=\"RIGHT_MIDDLE\">"
                       "<select id=\"%sHour\" name=\"%sHour\""
                       " onchange=\"setUTCFromLocalDateTimeForm('%s');",
-            Id,Id,Id);
+            Id,ParamName,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
@@ -441,10 +410,10 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
 	              "</td>");
 
    /***** Minute *****/
-   fprintf (Gbl.F.Out,"<td class=\"LEFT_MIDDLE\">"
+   fprintf (Gbl.F.Out,"<td class=\"CENTER_MIDDLE\">"
                       "<select id=\"%sMinute\" name=\"%sMinute\""
                       " onchange=\"setUTCFromLocalDateTimeForm('%s');",
-	    Id,Id,Id);
+	    Id,ParamName,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
@@ -464,7 +433,7 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
    fprintf (Gbl.F.Out,"<td class=\"LEFT_MIDDLE\">"
                       "<select id=\"%sSecond\" name=\"%sSecond\""
                       " onchange=\"setUTCFromLocalDateTimeForm('%s');",
-	    Id,Id,Id);
+	    Id,ParamName,Id);
    if (SubmitFormOnChange)
       fprintf (Gbl.F.Out,"document.getElementById('%s').submit();",
                Gbl.FormId);
@@ -486,7 +455,7 @@ static void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
 
    /***** Hidden field with UTC time (seconds since 1970) used to send time *****/
    fprintf (Gbl.F.Out,"<input type=\"hidden\" id=\"%sTimeUTC\" name=\"%sTimeUTC\" value=\"%ld\" />",
-            Id,Id,(long) TimeUTC);
+            Id,ParamName,(long) TimeUTC);
 
    /***** Script to set selectors to local date and time from UTC time *****/
    fprintf (Gbl.F.Out,"<script type=\"text/javascript\">"
@@ -1137,54 +1106,3 @@ void Dat_AssignDate (struct Date *DateDst,struct Date *DateSrc)
    DateDst->Day   = DateSrc->Day;
    DateDst->Week  = DateSrc->Week;
   }
-
-/*****************************************************************************/
-/****************************** Compare dates ********************************/
-/*****************************************************************************/
-// Return <0 if Date1<Date2
-// Return >0 if Date1>Date2
-// Return  0 if Date1==Date2
-
-int Dat_CompareDates (struct Date *Date1,struct Date *Date2)
-  {
-   if (Date1->Year  < Date2->Year ) return -1;
-   if (Date1->Year  > Date2->Year ) return 1;
-
-   if (Date1->Month < Date2->Month) return -1;
-   if (Date1->Month > Date2->Month) return 1;
-
-   if (Date1->Day   < Date2->Day  ) return -1;
-   if (Date1->Day   > Date2->Day  ) return 1;
-
-   return 0;
-  }
-
-/*****************************************************************************/
-/************************** Compare datetimes ********************************/
-/*****************************************************************************/
-// Return <0 if DateTime1<DateTime2
-// Return >0 if DateTime1>DateTime2
-// Return  0 if DateTime1==DateTime2
-
-int Dat_CompareDateTimes (struct DateTime *DateTime1,struct DateTime *DateTime2)
-  {
-   if (DateTime1->Date.Year   < DateTime2->Date.Year  ) return -1;
-   if (DateTime1->Date.Year   > DateTime2->Date.Year  ) return 1;
-
-   if (DateTime1->Date.Month  < DateTime2->Date.Month ) return -1;
-   if (DateTime1->Date.Month  > DateTime2->Date.Month ) return 1;
-
-   if (DateTime1->Date.Day    < DateTime2->Date.Day   ) return -1;
-   if (DateTime1->Date.Day    > DateTime2->Date.Day   ) return 1;
-
-   if (DateTime1->Time.Hour   < DateTime2->Time.Hour  ) return -1;
-   if (DateTime1->Time.Hour   > DateTime2->Time.Hour  ) return 1;
-
-   if (DateTime1->Time.Minute < DateTime2->Time.Minute) return -1;
-   if (DateTime1->Time.Minute > DateTime2->Time.Minute) return 1;
-
-   if (DateTime1->Time.Second < DateTime2->Time.Second) return -1;
-   if (DateTime1->Time.Second > DateTime2->Time.Second) return 1;
-
-   return 0;
-  }
diff --git a/swad_date.h b/swad_date.h
index 3f6d491fc..56a2fae61 100644
--- a/swad_date.h
+++ b/swad_date.h
@@ -70,7 +70,6 @@ void Dat_GetAndConvertCurrentDateTime (void);
 
 time_t Dat_GetUNIXTimeFromStr (const char *Str);
 bool Dat_GetDateFromYYYYMMDD (struct Date *Date,const char *YYYYMMDDString);
-bool Dat_GetDateTimeFromYYYYMMDDHHMMSS (struct DateTime *DateTime,const char *YYYYMMDDHHMMSS);
 
 void Dat_ShowClientLocalTime (void);
 
@@ -80,6 +79,11 @@ void Dat_ConvDateToDateStr (struct Date *Date,char *DateStr);
 void Dat_PutFormStartEndClientLocalDateTimesWithYesterdayToday (void);
 void Dat_PutFormStartEndClientLocalDateTimes (time_t TimeUTC[2]);
 
+void Dat_WriteFormClientLocalDateTimeFromTimeUTC (const char *Id,
+                                                  const char *ParamName,
+                                                  time_t TimeUTC,
+                                                  unsigned FirstYear,unsigned LastYear,
+                                                  bool SubmitFormOnChange,bool Disabled);
 time_t Dat_GetTimeUTCFromForm (const char *ParamName);
 
 void Dat_WriteFormDate (unsigned FirstYear,unsigned LastYear,
@@ -116,7 +120,4 @@ unsigned Dat_GetDayOfYear (struct Date *Date);
 void Dat_CalculateWeekOfYear (struct Date *Date);
 void Dat_AssignDate (struct Date *DateDst,struct Date *DateSrc);
 
-int Dat_CompareDates (struct Date *Date1,struct Date *Date2);
-int Dat_CompareDateTimes (struct DateTime *DateTime1,struct DateTime *DateTime2);
-
 #endif
diff --git a/swad_global.c b/swad_global.c
index baa4c42e0..90d7d8678 100644
--- a/swad_global.c
+++ b/swad_global.c
@@ -327,12 +327,7 @@ void Gbl_InitializeGlobals (void)
    Gbl.CurrentCrs.Grps.GrpTyp.MandatoryEnrollment = true;
    Gbl.CurrentCrs.Grps.GrpTyp.MultipleEnrollment = false;
    Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened = false;
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Year   =
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Month  =
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Day    =
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Hour   =
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Minute =
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Second = 0;
+   Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC = (time_t) 0;
    Gbl.CurrentCrs.Grps.GrpCod = -1L; // -1L stands for the whole course
    Gbl.CurrentCrs.Grps.GrpName[0] = '\0';
    Gbl.CurrentCrs.Grps.MaxStudents = INT_MAX;
diff --git a/swad_group.c b/swad_group.c
index c152113c6..3ca38ed8f 100644
--- a/swad_group.c
+++ b/swad_group.c
@@ -89,7 +89,7 @@ static bool Grp_GetIfGrpIsAvailable (long GrpTypCod);
 static void Grp_GetLstCodGrpsUsrBelongs (long CrsCod,long GrpTypCod,long UsrCod,
                                          struct ListCodGrps *LstGrps);
 static bool Grp_CheckIfGrpIsInList (long GrpCod,struct ListCodGrps *LstGrps);
-static bool Grp_CheckIfOpenTimeInTheFuture (struct DateTime *OpenTime);
+static bool Grp_CheckIfOpenTimeInTheFuture (time_t OpenTimeUTC);
 static bool Grp_CheckIfGroupTypeNameExists (const char *GrpTypName,long GrpTypCod);
 static bool Grp_CheckIfGroupNameExists (long GrpTypCod,const char *GrpName,long GrpCod);
 static void Grp_CreateGroupType (void);
@@ -1123,15 +1123,17 @@ static void Grp_ListGroupTypesForEdition (void)
    extern const char *Txt_The_groups_will_automatically_open;
    extern const char *Txt_The_groups_will_not_automatically_open;
    unsigned NumGrpTyp;
+   unsigned UniqueId;
+   char Id[32];
 
    /***** Write heading *****/
    Lay_StartRoundFrameTable (NULL,2,Txt_Types_of_group);
    Grp_WriteHeadingGroupTypes ();
 
    /***** List group types with forms for edition *****/
-   for (NumGrpTyp = 0;
+   for (NumGrpTyp = 0, UniqueId=1;
 	NumGrpTyp < Gbl.CurrentCrs.Grps.GrpTypes.Num;
-	NumGrpTyp++)
+	NumGrpTyp++, UniqueId++)
      {
       /* Put icon to remove group type */
       fprintf (Gbl.F.Out,"<tr>"
@@ -1218,14 +1220,13 @@ static void Grp_ListGroupTypesForEdition (void)
         	                                                                  Txt_The_groups_will_not_automatically_open,
                Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumGrpTyp].MustBeOpened ? Txt_The_groups_will_automatically_open :
         	                                                                  Txt_The_groups_will_not_automatically_open);
-      Dat_WriteFormDate (Gbl.Now.Date.Year,Gbl.Now.Date.Year + 1,"Open",
-                         &(Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumGrpTyp].OpenTime.Date),
-                         true,false);
-      fprintf (Gbl.F.Out,"</td>"
-                         "<td class=\"LEFT_MIDDLE\">");
-      Dat_WriteFormHourMinute ("OpenHour","OpenMinute",
-		               &(Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumGrpTyp].OpenTime.Time),
-                               true,false);
+      sprintf (Id,"open_time_%u",UniqueId);
+      Dat_WriteFormClientLocalDateTimeFromTimeUTC (Id,
+                                                   "Open",
+						   Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumGrpTyp].OpenTimeUTC,
+						   Gbl.Now.Date.Year,
+						   Gbl.Now.Date.Year + 1,
+						   true,false);
       fprintf (Gbl.F.Out,"</td>"
 	                 "</tr>"
 	                 "</table>");
@@ -1913,6 +1914,7 @@ static void Grp_WriteGrpHead (struct GroupType *GrpTyp)
    extern const char *Txt_Max_BR_students;
    extern const char *Txt_Students_ABBREVIATION;
    extern const char *Txt_Vacants;
+   static unsigned UniqueId = 0;
 
    /***** Name of group type *****/
    fprintf (Gbl.F.Out,"<tr>"
@@ -1921,10 +1923,15 @@ static void Grp_WriteGrpHead (struct GroupType *GrpTyp)
 	    GrpTyp->GrpTypName);
    if (GrpTyp->MustBeOpened)
      {
-      fprintf (Gbl.F.Out,"<br />%s: ",Txt_Opening_of_groups);
-      Dat_WriteDate (GrpTyp->OpenTime.YYYYMMDDHHMMSS);
-      fprintf (Gbl.F.Out,"&nbsp;");
-      Dat_WriteHourMinute (&(GrpTyp->OpenTime.YYYYMMDDHHMMSS[8]));
+      UniqueId++;
+      fprintf (Gbl.F.Out,"<br />%s: "
+                         "<span id=\"open_time_%u\"></span>"
+                         "<script type=\"text/javascript\">"
+                         "writeLocalDateTimeFromUTC('open_time_%u',%ld,'&nbsp;');"
+                         "</script>",
+               Txt_Opening_of_groups,
+               UniqueId,
+               UniqueId,(long) GrpTyp->OpenTimeUTC);
      }
    fprintf (Gbl.F.Out,"</td>"
                       "</tr>");
@@ -2097,12 +2104,12 @@ static void Grp_PutFormToCreateGroupType (void)
    fprintf (Gbl.F.Out,"<td class=\"LEFT_MIDDLE\">"
 	              "<table class=\"CELLS_PAD_2\">"
                       "<tr>"
-                      "<td class=\"LEFT_MIDDLE\">"
+                      "<td class=\"LEFT_MIDDLE\" style=\"width:20px;\">"
                       "<img src=\"%s/%s16x16.gif\""
                       " alt=\"%s\" title=\"%s\""
                       " class=\"ICON16x16\" />"
                       "</td>"
-	              "<td class=\"LEFT_BOTTOM\" style=\"width:20px;\">",
+	              "<td class=\"LEFT_MIDDLE\">",
             Gbl.Prefs.IconsURL,
             Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened ? "time" :
         	                                      "time-off",
@@ -2110,14 +2117,12 @@ static void Grp_PutFormToCreateGroupType (void)
         	                                      Txt_The_groups_will_not_automatically_open,
             Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened ? Txt_The_groups_will_automatically_open :
         	                                      Txt_The_groups_will_not_automatically_open);
-   Dat_WriteFormDate (Gbl.Now.Date.Year,Gbl.Now.Date.Year + 1,"Open",
-                      &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date),
-                      false,false);
-   fprintf (Gbl.F.Out,"</td>"
-                      "<td class=\"LEFT_MIDDLE\">");
-   Dat_WriteFormHourMinute ("OpenHour","OpenMinute",
-                            &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time),
-                            false,false);
+   Dat_WriteFormClientLocalDateTimeFromTimeUTC ("open_time",
+                                                "Open",
+                                                Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC,
+                                                Gbl.Now.Date.Year,
+                                                Gbl.Now.Date.Year + 1,
+                                                false,false);
    fprintf (Gbl.F.Out,"</td>"
                       "</tr>"
                       "</table>"
@@ -2244,7 +2249,7 @@ void Grp_GetListGrpTypesInThisCrs (Grp_WhichGroupTypes_t WhichGroupTypes)
 	 sprintf (Query,"SELECT crs_grp_types.GrpTypCod,crs_grp_types.GrpTypName,"
 			"crs_grp_types.Mandatory,crs_grp_types.Multiple,"
 			"crs_grp_types.MustBeOpened,"
-			"DATE_FORMAT(crs_grp_types.OpenTime,'%%Y%%m%%d%%H%%i%%S'),"
+			"UNIX_TIMESTAMP(crs_grp_types.OpenTime),"
 			"COUNT(crs_grp.GrpCod)"
 			" FROM crs_grp_types,crs_grp"
 			" WHERE crs_grp_types.CrsCod='%ld'"
@@ -2257,7 +2262,7 @@ void Grp_GetListGrpTypesInThisCrs (Grp_WhichGroupTypes_t WhichGroupTypes)
 	 sprintf (Query,"(SELECT crs_grp_types.GrpTypCod,crs_grp_types.GrpTypName AS GrpTypName,"
 			"crs_grp_types.Mandatory,crs_grp_types.Multiple,"
 			"crs_grp_types.MustBeOpened,"
-			"DATE_FORMAT(crs_grp_types.OpenTime,'%%Y%%m%%d%%H%%i%%S'),"
+			"UNIX_TIMESTAMP(crs_grp_types.OpenTime),"
 			"COUNT(crs_grp.GrpCod)"
 			" FROM crs_grp_types,crs_grp"
 			" WHERE crs_grp_types.CrsCod='%ld'"
@@ -2266,7 +2271,9 @@ void Grp_GetListGrpTypesInThisCrs (Grp_WhichGroupTypes_t WhichGroupTypes)
 			" UNION "
 			"(SELECT GrpTypCod,GrpTypName,"
 			"Mandatory,Multiple,"
-			"MustBeOpened,DATE_FORMAT(OpenTime,'%%Y%%m%%d%%H%%i%%S'),'0'"
+			"MustBeOpened,"
+			"UNIX_TIMESTAMP(OpenTime),"
+			"'0'"
 			" FROM crs_grp_types WHERE CrsCod='%ld'"
 			" AND GrpTypCod NOT IN (SELECT GrpTypCod FROM crs_grp))"
 			" ORDER BY GrpTypName",
@@ -2309,10 +2316,9 @@ void Grp_GetListGrpTypesInThisCrs (Grp_WhichGroupTypes_t WhichGroupTypes)
          /* Groups of this type must be opened? (row[4]) */
          Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].MustBeOpened = (Str_ConvertToUpperLetter (row[4][0]) == 'Y');
 
-         /* Get open time (row[5] holds the open time in YYYYMMDDHHMMSS format) */
-         if (!(Dat_GetDateTimeFromYYYYMMDDHHMMSS (&(Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].OpenTime),row[5])))
-	    Lay_ShowErrorAndExit ("Error when reading open time.");
-         Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].MustBeOpened &= Grp_CheckIfOpenTimeInTheFuture (&(Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].OpenTime));
+         /* Get open time (row[5] holds the open time UTC) */
+         Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].OpenTimeUTC = Dat_GetUNIXTimeFromStr (row[5]);
+         Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].MustBeOpened &= Grp_CheckIfOpenTimeInTheFuture (Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].OpenTimeUTC);
 
          /* Number of groups of this type (row[6]) */
          if (sscanf (row[6],"%u",&Gbl.CurrentCrs.Grps.GrpTypes.LstGrpTypes[NumRow].NumGrps) != 1)
@@ -2545,7 +2551,7 @@ static void Grp_GetDataOfGroupTypeByCod (struct GroupType *GrpTyp)
    unsigned long NumRows;
 
    /***** Get data of a type of group from database *****/
-   sprintf (Query,"SELECT GrpTypName,Mandatory,Multiple,MustBeOpened,DATE_FORMAT(OpenTime,'%%Y%%m%%d%%H%%i%%S')"
+   sprintf (Query,"SELECT GrpTypName,Mandatory,Multiple,MustBeOpened,UNIX_TIMESTAMP(OpenTime)"
 	          " FROM crs_grp_types"
                   " WHERE CrsCod='%ld' AND GrpTypCod='%ld'",
             Gbl.CurrentCrs.Crs.CrsCod,GrpTyp->GrpTypCod);
@@ -2560,9 +2566,8 @@ static void Grp_GetDataOfGroupTypeByCod (struct GroupType *GrpTyp)
    strcpy (GrpTyp->GrpTypName,row[0]);
    GrpTyp->MandatoryEnrollment = (Str_ConvertToUpperLetter (row[1][0]) == 'Y');
    GrpTyp->MultipleEnrollment  = (Str_ConvertToUpperLetter (row[2][0]) == 'Y');
-   GrpTyp->MustBeOpened          = (Str_ConvertToUpperLetter (row[3][0]) == 'Y');
-   if (!(Dat_GetDateTimeFromYYYYMMDDHHMMSS (&(GrpTyp->OpenTime),row[4])))
-      Lay_ShowErrorAndExit ("Error when reading open time.");
+   GrpTyp->MustBeOpened        = (Str_ConvertToUpperLetter (row[3][0]) == 'Y');
+   GrpTyp->OpenTimeUTC = Dat_GetUNIXTimeFromStr (row[4]);
 
    /***** Free structure that stores the query result *****/
    DB_FreeMySQLResult (&mysql_res);
@@ -2942,9 +2947,11 @@ void Grp_GetLstCodGrpsWithFileZonesIBelong (struct ListCodGrps *LstGrps)
 
    /***** Get groups which I belong to from database *****/
    sprintf (Query,"SELECT crs_grp.GrpCod FROM crs_grp_types,crs_grp,crs_grp_usr"
-                  " WHERE crs_grp_types.CrsCod='%ld' AND crs_grp_types.GrpTypCod=crs_grp.GrpTypCod"
+                  " WHERE crs_grp_types.CrsCod='%ld'"
+                  " AND crs_grp_types.GrpTypCod=crs_grp.GrpTypCod"
                   " AND crs_grp.FileZones='Y'"
-                  " AND crs_grp.GrpCod=crs_grp_usr.GrpCod AND crs_grp_usr.UsrCod='%ld'"
+                  " AND crs_grp.GrpCod=crs_grp_usr.GrpCod"
+                  " AND crs_grp_usr.UsrCod='%ld'"
                   " ORDER BY crs_grp_types.GrpTypName,crs_grp.GrpName",
             Gbl.CurrentCrs.Crs.CrsCod,Gbl.Usrs.Me.UsrDat.UsrCod);
    LstGrps->NumGrps = (unsigned) DB_QuerySELECT (Query,&mysql_res,"can not get the groups which I belong to");
@@ -3000,8 +3007,11 @@ void Grp_GetNamesGrpsStdBelongsTo (long GrpTypCod,long UsrCod,char *GroupNames)
 
    /***** Get the names of groups which a user belongs to, from database *****/
    sprintf (Query,"SELECT crs_grp.GrpName FROM crs_grp,crs_grp_usr"
-                  " WHERE crs_grp.GrpTypCod='%ld' AND crs_grp.GrpCod=crs_grp_usr.GrpCod AND crs_grp_usr.UsrCod='%ld'"
-                  " ORDER BY crs_grp.GrpName",GrpTypCod,UsrCod);
+                  " WHERE crs_grp.GrpTypCod='%ld'"
+                  " AND crs_grp.GrpCod=crs_grp_usr.GrpCod"
+                  " AND crs_grp_usr.UsrCod='%ld'"
+                  " ORDER BY crs_grp.GrpName",
+            GrpTypCod,UsrCod);
    NumRows = DB_QuerySELECT (Query,&mysql_res,"can not get the names of groups a user belongs to");
 
    /***** Get the groups *****/
@@ -3046,15 +3056,8 @@ void Grp_RecFormNewGrpTyp (void)
    Gbl.CurrentCrs.Grps.GrpTyp.MultipleEnrollment = (Str_ConvertToUpperLetter (YN[0]) == 'Y');
 
    /* Get open time */
-   Dat_GetDateFromForm ("OpenDay","OpenMonth","OpenYear",
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Day),
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Month),
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Year));
-   Dat_GetHourMinuteFromForm ("OpenHour","OpenMinute",
-                              &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Hour),
-                              &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Minute));
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Second = 0;
-   Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened = Grp_CheckIfOpenTimeInTheFuture (&(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime));
+   Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC = Dat_GetTimeUTCFromForm ("OpenTimeUTC");
+   Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened = Grp_CheckIfOpenTimeInTheFuture (Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC);
 
    if (Gbl.CurrentCrs.Grps.GrpTyp.GrpTypName[0])	// If there's a group type name
      {
@@ -3082,16 +3085,14 @@ void Grp_RecFormNewGrpTyp (void)
 /**************** Check if the open time if in the future ********************/
 /*****************************************************************************/
 
-static bool Grp_CheckIfOpenTimeInTheFuture (struct DateTime *OpenTime)
+static bool Grp_CheckIfOpenTimeInTheFuture (time_t OpenTimeUTC)
   {
-   /***** If any part of the date is 0 ==> groups must no be opened *****/
-   if (OpenTime->Date.Year  == 0 ||
-       OpenTime->Date.Month == 0 ||
-       OpenTime->Date.Day   == 0)
+   /***** If open time is 0 ==> groups must no be opened *****/
+   if (OpenTimeUTC == (time_t) 0)
       return false;
 
    /***** Is open time in the future? *****/
-   return (Dat_CompareDateTimes (OpenTime,&(Gbl.Now)) >= 0);
+   return (OpenTimeUTC > Gbl.TimeStartExecution);
   }
 
 /*****************************************************************************/
@@ -3180,7 +3181,7 @@ static void Grp_CreateGroupType (void)
 
    /***** Create a new group type *****/
    sprintf (Query,"INSERT INTO crs_grp_types (CrsCod,GrpTypName,Mandatory,Multiple,MustBeOpened,OpenTime)"
-                  " VALUES ('%ld','%s','%c','%c','%c','%04u%02u%02u%02u%02u%02u')",
+                  " VALUES ('%ld','%s','%c','%c','%c',FROM_UNIXTIME('%ld'))",
             Gbl.CurrentCrs.Crs.CrsCod,Gbl.CurrentCrs.Grps.GrpTyp.GrpTypName,
             Gbl.CurrentCrs.Grps.GrpTyp.MandatoryEnrollment ? 'Y' :
         	                                             'N',
@@ -3188,12 +3189,7 @@ static void Grp_CreateGroupType (void)
         	                                            'N',
             Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened ? 'Y' :
         	                                      'N',
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Year,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Month,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Day,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Hour,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Minute,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Second);
+            (long) Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC);
    Gbl.CurrentCrs.Grps.GrpTyp.GrpTypCod = DB_QueryINSERTandReturnCode (Query,"can not create type of group");
 
    /***** Write success message *****/
@@ -3769,27 +3765,15 @@ void Grp_ChangeOpenTimeGrpTyp (void)
    Grp_GetDataOfGroupTypeByCod (&Gbl.CurrentCrs.Grps.GrpTyp);
 
    /***** Get open time *****/
-   Dat_GetDateFromForm ("OpenDay","OpenMonth","OpenYear",
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Day),
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Month),
-                        &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Year));
-   Dat_GetHourMinuteFromForm ("OpenHour","OpenMinute",
-                              &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Hour),
-                              &(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Minute));
-   Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Second = 0;
-   Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened = Grp_CheckIfOpenTimeInTheFuture (&(Gbl.CurrentCrs.Grps.GrpTyp.OpenTime));
+   Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC = Dat_GetTimeUTCFromForm ("OpenTimeUTC");
+   Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened = Grp_CheckIfOpenTimeInTheFuture (Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC);
 
    /***** Update of the table of types of group changing the old open time of enrollment by the new *****/
-   sprintf (Query,"UPDATE crs_grp_types SET MustBeOpened='%c',OpenTime='%04u%02u%02u%02u%02u%02u'"
+   sprintf (Query,"UPDATE crs_grp_types SET MustBeOpened='%c',OpenTime=FROM_UNIXTIME('%ld')"
                   " WHERE GrpTypCod='%ld'",
             Gbl.CurrentCrs.Grps.GrpTyp.MustBeOpened ? 'Y' :
         	                                      'N',
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Year,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Month,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Date.Day,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Hour,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Minute,
-            Gbl.CurrentCrs.Grps.GrpTyp.OpenTime.Time.Second,
+            (long) Gbl.CurrentCrs.Grps.GrpTyp.OpenTimeUTC,
             Gbl.CurrentCrs.Grps.GrpTyp.GrpTypCod);
    DB_QueryUPDATE (Query,"can not update enrollment type of a type of group");
 
diff --git a/swad_group.h b/swad_group.h
index f95ea3de1..5439ca56f 100644
--- a/swad_group.h
+++ b/swad_group.h
@@ -80,7 +80,7 @@ struct GroupType
    bool MandatoryEnrollment;				// Enrollment is mandatory?
    bool MultipleEnrollment;				// Enrollment is multiple?
    bool MustBeOpened;					// Groups must be opened?
-   struct DateTime OpenTime;				// Open groups automatically in this date-time. If == 0, don't open.
+   time_t OpenTimeUTC;					// Open groups automatically in this date-time. If == 0, don't open.
    unsigned NumGrps;					// Number of groups of this type
    struct Group *LstGrps;				// List of groups of this type
   };