TimestampObservable.java

        Observable.interval(100, TimeUnit.MILLISECONDS)
                .take(3)
                .timestamp()
                .subscribe(new Observer<Timed<Long>>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(Timed<Long> longTimed) {
                        System.out.println(longTimed);
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });