diff --git a/src/core/2.base.js b/src/core/2.base.js
index d7007de52..63ff1821d 100644
--- a/src/core/2.base.js
+++ b/src/core/2.base.js
@@ -1079,7 +1079,7 @@
                     case "%b":
                     case "%B":
                         for (j = 0; j < 12; ++j) {
-                            if (BI.Date._MN[j].substr(0, a[i].length).toLowerCase() == a[i].toLowerCase()) {
+                            if (BI.getMonthName(j).substr(0, a[i].length).toLowerCase() == a[i].toLowerCase()) {
                                 m = j;
                                 break;
                             }
@@ -1144,7 +1144,7 @@
                 if (a[i].search(/[a-zA-Z]+/) != -1) {
                     var t = -1;
                     for (j = 0; j < 12; ++j) {
-                        if (BI.Date._MN[j].substr(0, a[i].length).toLowerCase() == a[i].toLowerCase()) {
+                        if (BI.getMonthName(j).substr(0, a[i].length).toLowerCase() == a[i].toLowerCase()) {
                             t = j;
                             break;
                         }