private static long timeUnitToMillis(final int ruleAge, final TimeUnit timeUnit) {
        final long unitMs;
        switch (timeUnit) {
            case MINUTES:
                unitMs = MINUTE_MS;
                break;
            case HOURS:
                unitMs = HOUR_MS;
                break;
            case DAYS:
                unitMs = DAY_MS;
                break;
            case WEEKS:
                unitMs = WEEK_MS;
                break;
            case MONTHS:
                unitMs = AVG_MONTH_MS;
                break;
            case YEARS:
                unitMs = YEAR_MS;
                break;
            default:
                throw new IllegalStateException("Unexpected value: " + timeUnit);
        }
        return unitMs * ruleAge;
    }
Months/years are variable things so this is only approximate
for use in sorting
stroom-core-client/src/main/java/stroom/receive/rules/client/presenter/DataRetentionImpactRow.java