定时删除指定目录下的目录或文件，适合一些备份多日的文件删除，可按当前时间选保留天数，可将之前超出保留天数的文件删除。(Regularly delete the specified directory directory or file, suitable for some backup files for several days to delete, you can choose the current time to retain the number of days, may exceed the number of days prior to the deletion of the file.)