diff --git a/plugins/c9.abtesting/abtesting.js b/plugins/c9.abtesting/abtesting.js
index 04cfe261..44fc2b00 100644
--- a/plugins/c9.abtesting/abtesting.js
+++ b/plugins/c9.abtesting/abtesting.js
@@ -32,7 +32,7 @@ function main(options, imports, register) {
     function isUserCreatedAfter(experimentDate, user) {
         if (!user || !user.date_add)
             throw new Error("Expected: user");
-        var diffDays = (experimentDate - experimentDate.now()) / MS_PER_DAY;
+        var diffDays = (experimentDate - Date.now()) / MS_PER_DAY;
         if (diffDays > 20) {
             // Sanity check: new Date() takes zero-based month argument, one-based day argument
             throw new Error("Passed a date far in the future to isUserCreatedAfter()");
diff --git a/plugins/c9.ide.abtesting/abtesting.js b/plugins/c9.ide.abtesting/abtesting.js
index c1747bf8..1a7160db 100644
--- a/plugins/c9.ide.abtesting/abtesting.js
+++ b/plugins/c9.ide.abtesting/abtesting.js
@@ -47,7 +47,7 @@ define(function(require, exports, module) {
         }
         
         function isUserCreatedAfter(experimentDate) {
-            var diffDays = (experimentDate - experimentDate.now()) / MS_PER_DAY;
+            var diffDays = (experimentDate - Date.now()) / MS_PER_DAY;
             if (diffDays > 20) {
                 // Sanity check: new Date() takes zero-based month argument, one-based day argument
                 throw new Error("Passed a date far in the future to isUserCreatedAfter()");