You are creating a Date object, which is a representation of a certain point in the timeline. This means that it will have all the parts necessary to represent it correctly, including minutes and seconds and so on. Because you initialize it from a string containing only a part of the date, the missing data will be defaulted.
I assume you are then "printing" this Date object, but without actually specifying a format like you did when parsing it. Use the same SimpleDateFormat but call the reverse method, format(Date) as Holger suggested