diff --git a/test/helpers/common.js b/test/helpers/common.js
index <HASH>..<HASH> 100644
--- a/test/helpers/common.js
+++ b/test/helpers/common.js
@@ -7,6 +7,8 @@ var Readable = require('stream').Readable || require('readable-stream');
 var Writable = require('stream').Writable || require('readable-stream').Writable;
 
 function adjustDateByOffset(d, offset) {
+  d = (d instanceof Date) ? d : new Date();
+
   if (offset >= 1) {
     d.setMinutes(d.getMinutes() - offset);
   } else {
test: quick fix to helper.