public static long getMillToDay(Calendar cal,int dateT){
        if(dateT!=0){
            cal.set(Calendar.DATE, dateT);
        }
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        return cal.getTimeInMillis()/1000L;
    }
@param cal  Calendar
@param dateT Integer
@return  long
core/src/main/java/com/dtstack/flink/sql/util/DateUtil.java