Could you please tell me what time is the last bus from Emei city to Chengdu?

I'm taking the last bus from CD to Emei City on 16th Dec 2013 and back to CD the next day 17th Dec. At that time it is too late to book the return ticket for the next day. Will I be able to buy a ticket after visiting Emei mountain (at about 16:00). Thank you so much!