diff --git a/examples/spinbutton/js/datepicker-spinbuttons.js b/examples/spinbutton/js/datepicker-spinbuttons.js
index 9b6f54a222..7095b4618d 100644
--- a/examples/spinbutton/js/datepicker-spinbuttons.js
+++ b/examples/spinbutton/js/datepicker-spinbuttons.js
@@ -52,42 +52,7 @@ DatePickerSpinButtons.prototype.init = function () {
 };
 
 DatePickerSpinButtons.prototype.getDaysInMonth = function (year, month) {
-
-  if (typeof year !== 'number') {
-    year = this.year;
-  }
-
-  if (typeof month !== 'number') {
-    month = this.month;
-  }
-
-  switch (month) {
-
-    case 0:
-    case 2:
-    case 4:
-    case 6:
-    case 7:
-    case 9:
-    case 11:
-      return 31;
-
-    case 1:
-      return (((this.yearIndex % 4 === 0) && (this.yearIndex % 100 !== 0) && (this.yearIndex % 400 === 0)) ? 29 : 28);
-
-    case 3:
-    case 5:
-    case 8:
-    case 10:
-      return 30;
-
-    default:
-      break;
-
-  }
-
-  return -1;
-
+  return new Date(year, month + 1, 0).getDate();
 };
 
 DatePickerSpinButtons.prototype.updateDay = function (day) {
diff --git a/test/tests/spinbutton_datepicker.js b/test/tests/spinbutton_datepicker.js
index 7777979376..f0bab68adc 100644
--- a/test/tests/spinbutton_datepicker.js
+++ b/test/tests/spinbutton_datepicker.js
@@ -13,42 +13,7 @@ const valuesMonth = ['January', 'February', 'March', 'April', 'May', 'June', 'Ju
 
 
 var getDaysInMonth = function (year, month) {
-
-  if (typeof year !== 'number') {
-    year = this.year;
-  }
-
-  if (typeof month !== 'number') {
-    month = this.month;
-  }
-
-  switch (month) {
-
-    case 0:
-    case 2:
-    case 4:
-    case 6:
-    case 7:
-    case 9:
-    case 11:
-      return 31;
-
-    case 1:
-      return (((this.yearIndex % 4 === 0) && (this.yearIndex % 100 !== 0) && (this.yearIndex % 400 === 0)) ? 29 : 28);
-
-    case 3:
-    case 5:
-    case 8:
-    case 10:
-      return 30;
-
-    default:
-      break;
-
-  }
-
-  return -1;
-
+  return new Date(year, month + 1, 0).getDate();
 };
 
 var d = new Date();