diff --git a/module/task/model.php b/module/task/model.php
index 419103dcbe..3c45aba987 100755
--- a/module/task/model.php
+++ b/module/task/model.php
@@ -4505,9 +4505,9 @@ class taskModel extends model
         if(empty($execution) or empty($this->config->limitTaskDate)) return false;
         if(empty($execution->multiple)) $this->lang->execution->common = $this->lang->project->common;
 
-        if(!empty($estStarted) and $estStarted < $execution->begin) dao::$errors['estStarted'][] = $pre . sprintf($this->lang->task->error->beginLtExecution, $this->lang->execution->common, $execution->begin);
-        if(!empty($estStarted) and $estStarted > $execution->end)   dao::$errors['estStarted'][] = $pre . sprintf($this->lang->task->error->beginGtExecution, $this->lang->execution->common, $execution->end);
-        if(!empty($deadline) and $deadline > $execution->end)       dao::$errors['deadline'][]   = $pre . sprintf($this->lang->task->error->endGtExecution, $this->lang->execution->common, $execution->end);
-        if(!empty($deadline) and $deadline < $execution->begin)     dao::$errors['deadline'][]   = $pre . sprintf($this->lang->task->error->endLtExecution, $this->lang->execution->common, $execution->begin);
+        if(!empty($estStarted) and !helper::isZeroDate($estStarted) and $estStarted < $execution->begin) dao::$errors['estStarted'][] = $pre . sprintf($this->lang->task->error->beginLtExecution, $this->lang->execution->common, $execution->begin);
+        if(!empty($estStarted) and !helper::isZeroDate($estStarted) and $estStarted > $execution->end)   dao::$errors['estStarted'][] = $pre . sprintf($this->lang->task->error->beginGtExecution, $this->lang->execution->common, $execution->end);
+        if(!empty($deadline) and !helper::isZeroDate($deadline) and $deadline > $execution->end)       dao::$errors['deadline'][]   = $pre . sprintf($this->lang->task->error->endGtExecution, $this->lang->execution->common, $execution->end);
+        if(!empty($deadline) and !helper::isZeroDate($deadline) and $deadline < $execution->begin)     dao::$errors['deadline'][]   = $pre . sprintf($this->lang->task->error->endLtExecution, $this->lang->execution->common, $execution->begin);
     }
 }