public RequestBuilder setTimeZone(TimeZone timeZone) {
        converter.setTimeOffset(timeZone != null ? timeZone.getOffset(System.currentTimeMillis())
                                                 : ExpressionConverter.DEFAULT_TIME_OFFSET);
        return this;
    }
Sets the time zone to build the request for. This information is propagated to the time-based grouping
expressions so that the produced groups are reasonable for the given zone.

@param timeZone The time zone to set.
@return This, to allow chaining.
container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java