=== modified file 'dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/dhis2/dhis2.period.js'
--- dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/dhis2/dhis2.period.js	2014-05-06 04:09:19 +0000
+++ dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/dhis2/dhis2.period.js	2014-05-06 04:11:23 +0000
@@ -153,6 +153,10 @@
   calendar = calendar || dhis2.period.calendar;
   format = format || dhis2.period.DEFAULT_DATE_FORMAT;
 
+  if( typeof calendar === 'undefined' ) {
+    throw new Error('calendar parameter was not provided or is undefined, and no global dhis2.period.calendar instance exists.')
+  }
+
   $.extend(this, {
     calendar: calendar,
     format: format,