private static Boolean validateTimeZone(String timeZone) {
        Set timeZoneSet = new HashSet(Arrays.asList(TimeZone.getAvailableIDs()));
        return timeZoneSet.contains(timeZone);
    }
This is the parser class of incremental aggregation definition.
modules/siddhi-core/src/main/java/io/siddhi/core/util/parser/AggregationParser.java