diff --git a/public/javascripts/edu/course.js b/public/javascripts/edu/course.js
index 3428011b..8aed5e7a 100644
--- a/public/javascripts/edu/course.js
+++ b/public/javascripts/edu/course.js
@@ -733,6 +733,7 @@ $(function(){
         lang:'ch',
         format:'Y-m-d H:i',
         validateOnBlur:false,
+        step: 15,
         onSelectDate:function() {
             if($.trim($("input[name='exercise_end_time']").val()) == ""){
                 var date = new Date(Date.parse($("input[name='exercise_publish_time']").val().replace(/-/g, "/")));
@@ -751,6 +752,7 @@ $(function(){
         allowBlank:true,
         lang:'ch',
         format:'Y-m-d H:i',
+        step: 15,
         validateOnBlur:false
     });
 
@@ -759,6 +761,7 @@ $(function(){
             allowBlank:true,
             lang:'ch',
             format:'Y-m-d H:i',
+            step: 15,
             validateOnBlur:false,
             onSelectDate:function() {
                 if($.trim($($("input[name='exercise_end_time_group[]']")[i]).val()) == ""){
@@ -780,6 +783,7 @@ $(function(){
             allowBlank:true,
             lang:'ch',
             format:'Y-m-d H:i',
+            step: 15,
             validateOnBlur:false
         });
     });