Fix the check for a non value in the time update for original timezone.

clock.css

@@ -4,3 +4,6 @@ span p{
 select {
 	max-width: 95%;
 }
+.chkbox {
+  display: inline-block;
+}

clock.js

@@ -34,7 +34,7 @@ function startTime(){
                                          hour:'2-digit',
                                          minute:'2-digit',
                                          second:'2-digit',});
-  if(original_tz != null){  
+  if(original_tz){//Test if there is a non-null value for original_tz. If True then the part of the page this pertains to is being displayed.
     document.getElementById('time_original').innerHTML = current_time.toLocaleString('en-EN' ,{
                                            timeZone: original_tz,
                                            dateStyle:'long',
@@ -47,5 +47,5 @@ function startTime(){
                                            minute:'2-digit',
                                            second:'2-digit'});
   }
-  document.getElementById('JStz').innerHTML = current_tz;
+  //document.getElementById('JStz').innerHTML = current_tz;
 }

clock.php

@@ -9,8 +9,10 @@
     if(!isset($selectedTimezone)){
       //I don't have any error message set here. It will just reload the page.
     } else{
+      $origHour = date('O');
       $originalTZ = date_default_timezone_get();
       date_default_timezone_set($selectedTimezone);
+      $scriptHour = date('O');
       $scriptTZ = date_default_timezone_get();
     }
   } else{
@@ -52,6 +54,10 @@
           "</p><p> GMT". date("O T") .'</p></span>';
           date_default_timezone_set($scriptTZ);
         }
+        if($_POST['displayOffset']){
+          $tzDifferance = (-1 * ($origHour - $scriptHour)) * 0.01;
+          echo '<p>The difference between the timezones is ' . $tzDifferance . ' hours</p>';
+        }
       ?>
       <div class="tz_select">
         <p>
@@ -103,6 +109,10 @@
         <br/>
         <label for="originalTZ">Display original timezone</label>
         <input type="checkbox" name="originalTZ" value="origTZ">
+        <span class="chkbox>
+          <label for="displayOffset">Display offset of selected timezones</label>
+          <input type="checkbox" name="displayOffset" value="disOS"/>
+        </span>
       </form>
       <p id="JStz"><?php echo date("e");?></p>
     </div>