How to calculate time difference in Android?

/**
 * @author robert.hinds
 *
 * Utility class for helper methods
 */
public class Utility {

   
    public static String getDateDifference(Date thenDate){
        Calendar now = Calendar.getInstance();
        Calendar then = Calendar.getInstance();
        now.setTime(new Date());
        then.setTime(thenDate);

       
        // Get the represented date in milliseconds
        long nowMs = now.getTimeInMillis();
        long thenMs = then.getTimeInMillis();
       
        // Calculate difference in milliseconds
        long diff = nowMs - thenMs;
       
        // Calculate difference in seconds
        long diffMinutes = diff / (60 * 1000);
        long diffHours = diff / (60 * 60 * 1000);
        long diffDays = diff / (24 * 60 * 60 * 1000);

        if (diffMinutes<60){
            if (diffMinutes==1)
                return diffMinutes + " minute ago";
            else
                return diffMinutes + " minutes ago";
        } else if (diffHours<24){
            if (diffHours==1)
                return diffHours + " hour ago";
            else
                return diffHours + " hours ago";
        }else if (diffDays<30){
            if (diffDays==1)
                return diffDays + " day ago";
            else
                return diffDays + " days ago";
        }else {
            return "a long time ago..";
        }
    }
}