public DateTime parseToDateTime(Step step, long time) {
        switch (step) {
            case DAY:
                return YYYYMMDD.parseDateTime(String.valueOf(time));
            case HOUR:
                return YYYYMMDDHH.parseDateTime(String.valueOf(time));
            case MINUTE:
                return YYYYMMDDHHMM.parseDateTime(String.valueOf(time));
            case SECOND:
                return YYYYMMDDHHMMSS.parseDateTime(String.valueOf(time));
        }
        throw new UnexpectedException("Unexpected downsampling: " + step.name());
    }
Convert date in `yyyy-MM-dd HHmmss` style to `yyyyMMddHHmmss` no matter the precision. Such as, in day precision,
this covert `yyyy-MM-dd` style to `yyyyMMdd`.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/query/DurationUtils.java