public TimeZone getTimeZone() {
        if (timeZone == null) {
            timeZone = TimeZone.getDefault();
        }

        return timeZone;
    }
Returns the time zone for which this <code>CronExpression</code>
will be resolved.
server/core/src/main/java/com/ke/schedule/server/core/common/CronExpression.java