diff --git a/mod/assign/lang/en/assign.php b/mod/assign/lang/en/assign.php
index 06775e59e00..624e4d9e211 100644
--- a/mod/assign/lang/en/assign.php
+++ b/mod/assign/lang/en/assign.php
@@ -134,8 +134,8 @@ $string['currentattemptof'] = 'This is attempt {$a->attemptnumber} ( {$a->maxatt
 $string['cutoffdate'] = 'Cut-off date';
 $string['cutoffdatecolon'] = 'Cut-off date: {$a}';
 $string['cutoffdate_help'] = 'If set, the assignment will not accept submissions after this date without an extension.';
-$string['cutoffdatevalidation'] = 'The cut-off date cannot be earlier than the due date.';
-$string['cutoffdatefromdatevalidation'] = 'Cut-off date must be after the allow submissions from date.';
+$string['cutoffdatevalidation'] = 'Cut-off date cannot be earlier than the due date.';
+$string['cutoffdatefromdatevalidation'] = 'Cut-off date cannot be earlier than the allow submissions from date.';
 $string['defaultlayout'] = 'Restore default layout';
 $string['defaultsettings'] = 'Default assignment settings';
 $string['defaultsettings_help'] = 'These settings define the defaults for all new assignments.';
@@ -157,7 +157,7 @@ $string['submissionempty'] = 'Nothing was submitted';
 $string['submissionmodified'] = 'You have existing submission data. Please leave this page and try again.';
 $string['submissionmodifiedgroup'] = 'The submission has been modified by somebody else. Please leave this page and try again.';
 $string['duedatereached'] = 'The due date for this assignment has now passed';
-$string['duedatevalidation'] = 'Due date must be after the allow submissions from date.';
+$string['duedatevalidation'] = 'Due date cannot be earlier than the allow submissions from date.';
 $string['editattemptfeedback'] = 'Edit the grade and feedback for attempt number {$a}.';
 $string['editonline'] = 'Edit online';
 $string['editingpreviousfeedbackwarning'] = 'You are editing the feedback for a previous attempt. This is attempt {$a->attemptnumber} out of {$a->totalattempts}.';
diff --git a/mod/assign/mod_form.php b/mod/assign/mod_form.php
index ffb9a159402..4cfc9413b34 100644
--- a/mod/assign/mod_form.php
+++ b/mod/assign/mod_form.php
@@ -223,18 +223,18 @@ class mod_assign_mod_form extends moodleform_mod {
     public function validation($data, $files) {
         $errors = parent::validation($data, $files);
 
-        if ($data['allowsubmissionsfromdate'] && $data['duedate']) {
-            if ($data['allowsubmissionsfromdate'] > $data['duedate']) {
+        if (!empty($data['allowsubmissionsfromdate']) && !empty($data['duedate'])) {
+            if ($data['duedate'] < $data['allowsubmissionsfromdate']) {
                 $errors['duedate'] = get_string('duedatevalidation', 'assign');
             }
         }
-        if ($data['duedate'] && $data['cutoffdate']) {
-            if ($data['duedate'] > $data['cutoffdate']) {
+        if (!empty($data['cutoffdate']) && !empty($data['duedate'])) {
+            if ($data['cutoffdate'] < $data['duedate'] ) {
                 $errors['cutoffdate'] = get_string('cutoffdatevalidation', 'assign');
             }
         }
-        if ($data['allowsubmissionsfromdate'] && $data['cutoffdate']) {
-            if ($data['allowsubmissionsfromdate'] > $data['cutoffdate']) {
+        if (!empty($data['allowsubmissionsfromdate']) && !empty($data['cutoffdate'])) {
+            if ($data['cutoffdate'] < $data['allowsubmissionsfromdate']) {
                 $errors['cutoffdate'] = get_string('cutoffdatefromdatevalidation', 'assign');
             }
         }