private static long getStartTimeOfAggregatesForMonth(long currentTime, String timeZone) {
        ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(Instant.ofEpochMilli(currentTime),
                ZoneId.of(timeZone));
        return ZonedDateTime.of(zonedDateTime.getYear(), zonedDateTime.getMonthValue(), 1, 0, 0, 0, 0,
                ZoneId.of(timeZone)).toEpochSecond() * 1000;
    }
Performs time conversions related to incremental aggregation.
modules/siddhi-core/src/main/java/io/siddhi/core/util/IncrementalTimeConverterUtil.java