You received the official answer in the previous post. HOWEVER, as the census get older, remember that transportation was difficult. In many of the instructions for the census it does not state it will be taken on the date, but the family living in the dwelling will be listed on a certain date. This means that it may be days, weeks, or months later depending on the condition or presence of roads in the area of the census.
Some times you get lucky and the census taker will include the information as instructed but will include the date he actually visited the dwelling.
I have an interesting situation in the western Pennsylvania census in 1850. My Ancestor does not have a common last name. He appears at least twice, and possibly four times in the same census. He was in an occupation where he traveled from town to town. In the first entry he is recorded with a wife and child. In the other entries he is in different places living in boarding houses.