Applying L visa do I need to tell consular officer exact dates I will be entering and leaving PRC?

I am going on a backpacking trip and would like to include China in the mix. However, I do not have an exact date for when I will be entering and leaving PRC. I do have a planned out itinerary when i'm in the country though. I also know how i will be entering and leaving (enter through trans-mongolian railway, exit through shanghai-jeju flight).