public TimeZone getTimeZone() {
        return timeZone;
    }
Returns the {@link TimeZone} used when resolving time expressions such as {@link
com.yahoo.search.grouping.request.DayOfMonthFunction} and {@link com.yahoo.search.grouping.request.HourOfDayFunction}.

@return the time zone in use.
container-search/src/main/java/com/yahoo/search/grouping/GroupingRequest.java