Fix bug in setting names for months

src/NodaTimeSplitter.php

@@ -266,7 +266,7 @@ final class NodaTimeSplitter {
             );
 
             try {
-                return $prefix . $fmt->format(MD_STD::strtotime("{$moda[0]}-{$moda[2]}-10 01:01:01")) . $suffix;
+                return $prefix . $fmt->format(MD_STD::strtotime("{$moda[0]}-{$moda[2]}-15 01:01:01")) . $suffix;
             }
             catch (MDInvalidInputDate $e) {
                 return "";