diff --git a/client/js/api.js b/client/js/api.js
index 3d4787be..3623045b 100644
--- a/client/js/api.js
+++ b/client/js/api.js
@@ -1,6 +1,5 @@
 'use strict';
 
-require('./util/date.js');
 const cookies = require('js-cookie');
 const request = require('superagent');
 const config = require('./config.js');
diff --git a/client/js/util/date.js b/client/js/util/date.js
deleted file mode 100644
index 7a40b163..00000000
--- a/client/js/util/date.js
+++ /dev/null
@@ -1,7 +0,0 @@
-'use strict';
-
-Date.prototype.addDays = function(days) {
-    let dat = new Date(this.valueOf());
-    dat.setDate(dat.getDate() + days);
-    return dat;
-};
diff --git a/client/js/util/polyfill.js b/client/js/util/polyfill.js
index 91186b2a..71ee9724 100644
--- a/client/js/util/polyfill.js
+++ b/client/js/util/polyfill.js
@@ -59,3 +59,10 @@ Number.prototype.between = function(a, b, inclusive) {
 
 // non standard
 Promise.prototype.abort = () => {};
+
+// non standard
+Date.prototype.addDays = function(days) {
+    let dat = new Date(this.valueOf());
+    dat.setDate(dat.getDate() + days);
+    return dat;
+};