The CONVERT function is probably what you need. You can convert the datetime into a char or varchar in a predefined style. The styles are numbers from 0 to around 20 (give 2 digit years) or 100 to 120 (4 digit years). You can truncate the time off by setting the size of the char or varchar. The default style is 100, try some or find a reference. I find 100, 1 or 101, and 111 the most useful.
convert(varchar(11), someColumn, 101)