Index: lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/service/MonitoringService.java
===================================================================
diff -u -r66f472a982a10227afd93740142320f4be590c8a -rbaeb14be8e4c423b2e9ebe3a253c73499051f765
--- lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/service/MonitoringService.java	(.../MonitoringService.java)	(revision 66f472a982a10227afd93740142320f4be590c8a)
+++ lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/service/MonitoringService.java	(.../MonitoringService.java)	(revision baeb14be8e4c423b2e9ebe3a253c73499051f765)
@@ -812,30 +812,56 @@
 		.withDescription(scheduleGate.getTitle() + ":" + lessonName)
 		.usingJobData("gateId", scheduleGate.getActivityId()).build();
 
-	// create customized triggers
-	Trigger openGateTrigger = TriggerBuilder.newTrigger()
-		.withIdentity("openGateTrigger:" + scheduleGate.getActivityId())
-		.startAt(scheduleGate.getGateOpenTime(schedulingStartTime)).build();
+	// start the scheduling job
+	boolean startGateOnly = ((scheduleGate.getGateStartTimeOffset() == null)
+		&& (scheduleGate.getGateEndTimeOffset() == null))
+		|| ((scheduleGate.getGateStartTimeOffset() != null) && (scheduleGate.getGateEndTimeOffset() == null));
+	String openGateTriggerName = "openGateTrigger:" + scheduleGate.getActivityId();
+	String closeGateTriggerName = "closeGateTrigger:" + scheduleGate.getActivityId();
 
-	Trigger closeGateTrigger = TriggerBuilder.newTrigger()
-		.withIdentity("closeGateTrigger:" + scheduleGate.getActivityId())
-		.startAt(scheduleGate.getGateCloseTime(schedulingStartTime)).build();
+	Trigger openGateTrigger = null;
+	Trigger closeGateTrigger = null;
+	try {
+	    openGateTrigger = scheduler.getTrigger(TriggerKey.triggerKey(openGateTriggerName));
+	    closeGateTrigger = scheduler.getTrigger(TriggerKey.triggerKey(closeGateTriggerName));
+	} catch (SchedulerException e) {
+	    MonitoringService.log.error(
+		    "Error occurred at [runGateScheduler] - fail to start scheduling. Error while fetching Quartz trigger \""
+			    + openGateTriggerName + "\"",
+		    e);
+	}
 
-	// start the scheduling job
 	try {
-	    if (((scheduleGate.getGateStartTimeOffset() == null) && (scheduleGate.getGateEndTimeOffset() == null))
-		    || ((scheduleGate.getGateStartTimeOffset() != null)
-			    && (scheduleGate.getGateEndTimeOffset() == null))) {
+	    if (openGateTrigger != null) {
+		openGateTrigger = openGateTrigger.getTriggerBuilder()
+			.startAt(scheduleGate.getGateOpenTime(schedulingStartTime)).build();
+		scheduler.rescheduleJob(openGateTrigger.getKey(), openGateTrigger);
+	    } else {
+		// create customized triggers
+		openGateTrigger = TriggerBuilder.newTrigger().withIdentity(openGateTriggerName)
+			.startAt(scheduleGate.getGateOpenTime(schedulingStartTime)).build();
 		scheduler.scheduleJob(openScheduleGateJob, openGateTrigger);
-	    } else if (openGateTrigger.getStartTime().before(closeGateTrigger.getStartTime())) {
-		scheduler.scheduleJob(openScheduleGateJob, openGateTrigger);
-		scheduler.scheduleJob(closeScheduleGateJob, closeGateTrigger);
 	    }
 
+	    if (!startGateOnly) {
+		if (closeGateTrigger != null) {
+		    closeGateTrigger = closeGateTrigger.getTriggerBuilder()
+			    .startAt(scheduleGate.getGateCloseTime(schedulingStartTime)).build();
+		    scheduler.rescheduleJob(openGateTrigger.getKey(), closeGateTrigger);
+		} else {
+		    // create customized triggers
+		    closeGateTrigger = TriggerBuilder.newTrigger()
+			    .withIdentity("closeGateTrigger:" + scheduleGate.getActivityId())
+			    .startAt(scheduleGate.getGateCloseTime(schedulingStartTime)).build();
+		    scheduler.scheduleJob(closeScheduleGateJob, closeGateTrigger);
+		}
+	    }
 	} catch (SchedulerException e) {
-	    throw new MonitoringServiceException("Error occurred at [runGateScheduler] - fail to start scheduling", e);
+	    MonitoringService.log.error(
+		    "Error occurred at [runGateScheduler] - fail to start scheduling. Error while setting up gate open/close triggers. Open Gate Trigger name \""
+			    + openGateTriggerName + "\"",
+		    e);
 	}
-
 	if (MonitoringService.log.isDebugEnabled()) {
 	    MonitoringService.log.debug("Scheduler for Gate " + scheduleGate.getActivityId() + " started...");
 	}
Index: lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/web/GateController.java
===================================================================
diff -u -rf2ad75cef0c507a64877942631fee13efbc6ed50 -rbaeb14be8e4c423b2e9ebe3a253c73499051f765
--- lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/web/GateController.java	(.../GateController.java)	(revision f2ad75cef0c507a64877942631fee13efbc6ed50)
+++ lams_monitoring/src/java/org/lamsfoundation/lams/monitoring/web/GateController.java	(.../GateController.java)	(revision baeb14be8e4c423b2e9ebe3a253c73499051f765)
@@ -29,6 +29,7 @@
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Collection;
+import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -257,10 +258,15 @@
 	} else {
 	    gateForm.setActivityCompletionBased(false);
 	    Lesson lesson = learnerService.getLessonByActivity(scheduleGate);
-	    Calendar startingTime = new GregorianCalendar(TimeZone.getDefault());
-	    startingTime.setTime(lesson.getStartDateTime());
-	    startingTime.add(Calendar.MINUTE, scheduleGate.getGateStartTimeOffset().intValue());
-	    gateForm.setStartingTime(startingTime.getTime());
+	    Date lessonStartingTime = lesson.getStartDateTime();
+	    if (lessonStartingTime == null && Lesson.NOT_STARTED_STATE.equals(lesson.getLessonStateId())) {
+		// Assume the lesson will start at the scheduled time
+		lessonStartingTime = lesson.getScheduleStartDate();
+	    }
+	    Calendar gateStartingTime = new GregorianCalendar(TimeZone.getDefault());
+	    gateStartingTime.setTime(lessonStartingTime);
+	    gateStartingTime.add(Calendar.MINUTE, scheduleGate.getGateStartTimeOffset().intValue());
+	    gateForm.setStartingTime(gateStartingTime.getTime());
 	}
 
 	return "gate/scheduleGateContent";
Index: lams_monitoring/web/gate/scheduleGateContent.jsp
===================================================================
diff -u -r54007f98ca71e0073f19c5db78536437123287c6 -rbaeb14be8e4c423b2e9ebe3a253c73499051f765
--- lams_monitoring/web/gate/scheduleGateContent.jsp	(.../scheduleGateContent.jsp)	(revision 54007f98ca71e0073f19c5db78536437123287c6)
+++ lams_monitoring/web/gate/scheduleGateContent.jsp	(.../scheduleGateContent.jsp)	(revision baeb14be8e4c423b2e9ebe3a253c73499051f765)
@@ -54,26 +54,7 @@
 					shown = true;
 				}
 			}
-	/* 		
-			function applyDate() {
-				var date = $('#scheduleDatetimeField').val();
-				if (date) {
-					$.ajax({
-						url : LAMS_URL + 'monitoring/gate.do',
-						cache : false,
-						data : {
-							'method'        : ??,
-							'openDate' : date
-						},
-						success : function() {
-							refreshMonitor('lesson');
-						}
-					});
-				} else {
-					alert('<fmt:message key="error.lesson.schedule.date"/>');
-				}
-			}
-	 */	</script>
+		</script>
     </lams:head>
     
     <body class="stripes">
@@ -99,7 +80,7 @@
 							</a>
 							<%-- padding keeps the inputs the same height as the buttons. No flicking when shown/hidden --%>
 							<form:input cssClass="input input-sm" path="scheduleDate" id="scheduleDate" style="vertical-align:bottom"/> 
-							<input type="id" id="scheduleDatetimeApply" class="btn btn-primary btn-sm loffset2" value="<fmt:message key="button.apply"/>" />
+							<input type="submit" id="scheduleDatetimeApply" class="btn btn-primary btn-sm loffset2" value="<fmt:message key="button.apply"/>" />
 						</div>
 						</form:form>
 					</c:if>