diff --git a/application/models/Blocked_periods_model.php b/application/models/Blocked_periods_model.php
index 73089aad..5b31119d 100644
--- a/application/models/Blocked_periods_model.php
+++ b/application/models/Blocked_periods_model.php
@@ -83,10 +83,21 @@ class Blocked_periods_model extends EA_Model {
         // Make sure all required fields are provided.
         if (
             empty($blocked_period['name'])
+            || empty($blocked_period['start_datetime'])
+            || empty($blocked_period['end_datetime'])
         )
         {
             throw new InvalidArgumentException('Not all required fields are provided: ' . print_r($blocked_period, TRUE));
         }
+
+        // Make sure that the start date time is before the end. 
+        $start_date_time_object = new DateTime($blocked_period['start_datetime']);
+        $end_date_time_object = new DateTime($blocked_period['end_datetime']);
+
+        if ($start_date_time_object >= $end_date_time_object)
+        {
+            throw new InvalidArgumentException('The start must be before the end date time value.');
+        }
     }
 
     /**
diff --git a/assets/js/pages/blocked_periods.js b/assets/js/pages/blocked_periods.js
index 647e4741..a158d44e 100644
--- a/assets/js/pages/blocked_periods.js
+++ b/assets/js/pages/blocked_periods.js
@@ -261,6 +261,15 @@ App.Pages.BlockedPeriods = (function () {
                 throw new Error(lang('fields_are_required'));
             }
 
+            const startDateTimeObject = App.Utils.UI.getDatetimepickerValue($startDateTime);
+            const endDateTimeObject = App.Utils.UI.getDatetimepickerValue($endDateTime);
+
+            if (startDateTimeObject >= endDateTimeObject) {
+                $startDateTime.addClass('is-invalid');
+                $endDateTime.addClass('is-invalid');
+                throw new Error(lang('start_date_before_end_error'));
+            }
+
             return true;
         } catch (error) {
             $blockedPeriods.find('.form-message').addClass('alert-danger').text(error.message).show();