Just to check what is the time of tidal boar on Sat, 6 Sep and Sat 13 Sep 2014 ? @Qiantang River

The mid time of the lunar August is the best to time to see the tidal.
The exact time is hard to predict in such an early time.
But according to the situation in last year and this year's lunar calender, you can go to see the tidal any date during your visiting.
I suggest you to ask again here on this website in around late August to confirm the exact day.