diff --git a/htdocs/core/lib/date.lib.php b/htdocs/core/lib/date.lib.php
index 9159438fd87..afa5d6079fc 100644
--- a/htdocs/core/lib/date.lib.php
+++ b/htdocs/core/lib/date.lib.php
@@ -595,7 +595,7 @@ function dol_get_next_week($day, $week, $month, $year)
  *                                                                              True or 1 or 'gmt' to compare with GMT date.
  *                                                                              Example: dol_get_first_day(1970,1,false) will return -3600 with TZ+1, a dol_print_date on it will return 1970-01-01 00:00:00
  *                                                                              Example: dol_get_first_day(1970,1,true) will return 0 whatever is TZ, a dol_print_date on it will return 1970-01-01 00:00:00
- *  @return		int|string				Date as a timestamp, '' if error
+ *  @return		int|''				Date as a timestamp, '' if error
  */
 function dol_get_first_day($year, $month = 1, $gm = false)
 {
@@ -614,7 +614,7 @@ function dol_get_first_day($year, $month = 1, $gm = false)
  * 	@param		int			$month		Month
  * 	@param		bool|int<0,1>|'gmt'|'tzserver'|'tzref'|'tzuser'|'tzuserrel'	$gm		False or 0 or 'tzserver' = Return date to compare with server TZ,
  *                                                                                  True or 1 or 'gmt' to compare with GMT date.
- *	@return		int|string				Date as a timestamp, '' if error
+ *	@return		int|''					Date as a timestamp, '' if error
  */
 function dol_get_last_day($year, $month = 12, $gm = false)
 {
diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 5f1f9496d5f..0f49eebe26b 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -3904,7 +3904,7 @@ function dol_getdate($timestamp, $fast = false, $forcetimezone = '')
  *										'tzuserrel' = local to user TZ taking dst into account at the given date. Use this one to convert date input from user into a GMT date.
  *										'tz,TimeZone' = use specified timezone
  *	@param	int			$check			0=No check on parameters (Can use day 32, etc...)
- *	@return	int|string					Date as a timestamp, '' if error
+ *	@return	int|''						Date as a timestamp, '' if error
  * 	@see 								dol_print_date(), dol_stringtotime(), dol_getdate()
  */
 function dol_mktime($hour, $minute, $second, $month, $day, $year, $gm = 'auto', $check = 1)
diff --git a/htdocs/projet/element.php b/htdocs/projet/element.php
index 7d03c54a5b6..5ecd7788178 100644
--- a/htdocs/projet/element.php
+++ b/htdocs/projet/element.php
@@ -178,13 +178,6 @@ if ($id == '' && $ref == '') {
 	exit();
 }
 
-if ($dates === '') {
-	$dates = null;
-}
-if ($datee === '') {
-	$datee = null;
-}
-
 $mine = GETPOST('mode') == 'mine' ? 1 : 0;
 //if (! $user->rights->projet->all->lire) $mine=1;	// Special for projects
 
@@ -766,10 +759,10 @@ if (!$showdatefilter) {
 	print '<input type="hidden" name="tablename" value="'.(empty($tablename) ? '' : $tablename).'">';
 	print '<input type="hidden" name="action" value="view">';
 	print '<div class="inline-block">';
-	print $form->selectDate((int) $dates, 'dates', 0, 0, 1, '', 1, 0, 0, '', '', '', '', 1, '', $langs->trans("From"));
+	print $form->selectDate($dates, 'dates', 0, 0, 1, '', 1, 0, 0, '', '', '', '', 1, '', $langs->trans("From"));
 	print '</div>';
 	print '<div class="inline-block">';
-	print $form->selectDate((int) $datee, 'datee', 0, 0, 1, '', 1, 0, 0, '', '', '', '', 1, '', $langs->trans("to"));
+	print $form->selectDate($datee, 'datee', 0, 0, 1, '', 1, 0, 0, '', '', '', '', 1, '', $langs->trans("to"));
 	print '</div>';
 	print '<div class="inline-block">';
 	print '<input type="submit" name="refresh" value="'.$langs->trans("Refresh").'" class="button small">';
@@ -804,11 +797,10 @@ foreach ($listofreferent as $key => $value) {
 	$name = $langs->trans($value['name']);
 	$qualified = $value['test'];
 	$margin = empty($value['margin']) ? '' : $value['margin'];
-	if ($qualified && isset($margin)) {		// If this element must be included into profit calculation ($margin is 'minus' or 'add')
+	if ($qualified && $margin) {		// If this element must be included into profit calculation ($margin is 'minus' or 'add')
 		if ($margin === 'add') {
 			$tooltiponprofitplus .= ' &gt; '.$name." (+)<br>\n";
-		}
-		if ($margin === 'minus') {
+		} elseif ($margin === 'minus') {
 			$tooltiponprofitminus .= ' &gt; '.$name." (-)<br>\n";
 		}
 	}
@@ -853,7 +845,7 @@ foreach ($listofreferent as $key => $value) {
 	$qualified = $value['test'];
 	$margin = empty($value['margin']) ? 0 : $value['margin'];
 	$project_field = empty($value['project_field']) ? '' : $value['project_field'];
-	if ($qualified && isset($margin)) {		// If this element must be included into profit calculation ($margin is 'minus' or 'add')
+	if ($qualified) {		// If this element must be included into profit summary table ($margin is '', 'minus' or 'add')
 		$element = new $classname($db);
 
 		$elementarray = $object->get_element_list($key, $tablename, $datefieldname, $dates, $datee, !empty($project_field) ? $project_field : 'fk_projet');