Utils: update date-util.js (#22099)

Co-authored-by: xulongtai <xulongtai@ganguo.hk>

src/utils/date-util.js

@@ -48,19 +48,9 @@ export const parseDate = function(string, format) {
 };
 
 export const getDayCountOfMonth = function(year, month) {
-  if (month === 3 || month === 5 || month === 8 || month === 10) {
-    return 30;
-  }
-
-  if (month === 1) {
-    if (year % 4 === 0 && year % 100 !== 0 || year % 400 === 0) {
-      return 29;
-    } else {
-      return 28;
-    }
-  }
+  if (isNaN(+month)) return 31;
 
-  return 31;
+  return new Date(year, +month + 1, 0).getDate();
 };
 
 export const getDayCountOfYear = function(year) {