Jinshanling in May/June 2015 - Sunset

Hi,
Hi, I intend to visit the section of the wall this coming end-May.
Can you advise, what time is sunset during this time of the year ?
Also, is there a closing time where visitor must get out from the wall ?
Which vantage point (such as tower) is a good place to take good sunset photos ?

Thanks!NL.