Added example that updates existing check_date tags.

esample_code.js

@@ -60,4 +60,23 @@ for (var key in Iterator(new java.util.HashSet(tags.keySet()))) {
     }
   }
 }
+tags.remove('automatic_check_date');"
+
+// example 
+// update existing check_date tags
+//
+// NOTE: actually doing this is likely a bad idea
+//
+function addCheckDate(key) {
+  df = new java.text.SimpleDateFormat('yyyy-MM-dd');
+  v = new java.util.ArrayList();
+  v.add(df.format(new java.util.Date()));
+  tags.put('check_date:'+key,v);
+}
+
+for (var key in Iterator(new java.util.HashSet(tags.keySet()))) {
+  if (key.startsWith('check_date')) {
+    addCheckDate(key);
+  }
+}
 tags.remove('automatic_check_date');"

example_master_preset.xml

@@ -75,5 +75,26 @@ for (var key in Iterator(new java.util.HashSet(tags.keySet()))) {
 tags.remove('automatic_check_date');"
         	text="Automatic check_date generation"/>	
 		</item> <!-- check_date example all changed -->
+		<item name="check_date example update existing" icon="" type="node,way,closedway,relation" preset_name_label="true">
+            <link href="http://wiki.openstreetmap.org/wiki/Key:check_date" />
+            <!-- originalTags and tags are java.util.Map<String,ArrayList<String>>, originalTags are the tags 
+                 before the PropertyEditor was started, tags are the current values, by removing the key at the 
+                 end of the script it can be re-run without manually reseting the value, &, <, > need to be escaped -->
+        	<text key="automatic_check_date" javascript="
+function addCheckDate(key) {
+  df = new java.text.SimpleDateFormat('yyyy-MM-dd');
+  v = new java.util.ArrayList();
+  v.add(df.format(new java.util.Date()));
+  tags.put(key,v);
+}
+
+for (var key in Iterator(new java.util.HashSet(tags.keySet()))) {
+  if (key.startsWith('check_date')) {
+    addCheckDate(key);
+  }
+}
+tags.remove('automatic_check_date');"
+        	text="Automatic check_date generation"/>	
+		</item> <!-- check_date example update existing -->
     </group> <!-- check_date examples -->
 </presets>