Why is my Date value recognized as a string?

The value I have for mCreationDate in this exercise is being interpreted as a String.

To my eyes every point of the code labels the type as a Date. Can you see what's causing the error?

File Example.java

import java.util.Date; import com.teamtreehouse.Treet;

public class Example {

public static void main(String[] args){

Treet treet = new Treet("craigdennis",
                       "Want to be famous? Tweet about Java with #treet!",
                       "tweet",
                        new Date(1421849732000L)
                       );
System.out.printf("This is a new Treet: %s %n", treet);  

}

}

File Treet.java

public class Treet {

private String mAuthor; private String mTitle; private String mDescription; private Date mCreationDate = new Date();

public Treet ( String author, String title, String description, Date creationDate){

mAuthor = author;
mDescription = creationDate;
mTitle = title;
mCreationDate = creationDate;

}

public String getAuthor(){ return mAuthor; } public String getmDescription() { return mDescription; } public String getmTitle() { return mTitle; } public Date mCreationDate() { return mCreationDate; }

}