What is the exact departure time of K23

Hi, I have been searching for information of K23 from Beijing to Ulaanbater. Surprised that there's a lot of different information about the departure date and time. I have heard K23 departs every Tuesday all year round but not sure about the time. Some said it departs at 07:45 while many other sources said it like 11:22 or 11:55 or even 08:05. So I would like to know the exact and most updated departure date and time. I'm going there around may2015. Thank you for your help in advance. Gratitude from Thailand.