fix web file-list last_modified wrong date bug. (#440)

src/webapp/src/utils/common.ts

@@ -112,7 +112,7 @@ class Utils {
     static timestampToHumanReadable(timestamp: number): string {
         const date = new Date(timestamp * 1000);
         const year = date.getFullYear().toString().padStart(4, "0");
-        const month = date.getMonth().toString().padStart(2, "0");
+        const month = (date.getMonth() + 1).toString().padStart(2, "0");
         const day = date.getDate().toString().padStart(2, "0");
         const hour = date.getHours().toString().padStart(2, "0");
         const min = date.getMinutes().toString().padStart(2, "0");