cdm/src/main/java/uk/ac/rdg/resc/edal/time/FixedYearLengthChronology.java
@Override
    public final Chronology withZone(DateTimeZone zone) {
        if (zone.equals(DateTimeZone.UTC)) return this.withUTC();
        throw new UnsupportedOperationException("Not supported yet.");
    }
@Override
    public final Chronology withZone(DateTimeZone zone) {
        if (zone.equals(DateTimeZone.UTC)) return this.withUTC();
        throw new UnsupportedOperationException("Not supported yet.");
    }
Throws UnsupportedOperationException unless the time zone is UTC