Java date utility class instance sharing

public final class DateUtils {

public static String FORMAT_SHORT = "yyyy-MM-dd";

public static String FORMAT_LONG = "yyyy-MM-dd HH:mm:ss";

public static String FORMAT_FULL = "yyyy-MM-dd HH:mm:ss.S";

public static String FORMAT_SHORT_CN = "yyyy years MM month dd";

public static String FORMAT_LONG_CN = "yyyy years MM month dd day   HH when mm points ss seconds ";

public static String FORMAT_FULL_CN = "yyyy years MM month dd day   HH when mm points ss seconds SSS ms ";

public static String getDatePattern() {
return FORMAT_LONG;
}

public static String getNow() {
return format(new Date());
}

public static String getNow(String format) {
return format(new Date(), format);
}

public static String format(Date date) {
return format(date, getDatePattern());
}

public static String format(Date date, String pattern) {
String returnValue = "";
if (date != null) {
SimpleDateFormat df = new SimpleDateFormat(pattern);
returnValue = df.format(date);
}
return (returnValue);
}

public static Date parse(String strDate) {
return parse(strDate, getDatePattern());
}

public static Date parse(String strDate, String pattern) {
SimpleDateFormat df = new SimpleDateFormat(pattern);
try {
return df.parse(strDate);
} catch (ParseException e) {
e.printStackTrace();
return null;
}
}

public static Date addMonth(Date date, int n) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, n);
return cal.getTime();
}

public static Date addDay(Date date, int n) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, n);
return cal.getTime();
}

public static String getTimeString() {
SimpleDateFormat df = new SimpleDateFormat(FORMAT_FULL);
Calendar calendar = Calendar.getInstance();
return df.format(calendar.getTime());
}

public static String getYear(Date date) {
return format(date).substring(0, 4);
}

public static int countDays (String date) {
long t = Calendar.getInstance().getTime().getTime();
Calendar c = Calendar.getInstance();
c.setTime(parse(date));
long t1 = c.getTime().getTime();
return (int)(t/1000 - t1/1000)/3600/24;
}

public static int countDays (String date, String format) {
long t = Calendar.getInstance().getTime().getTime();
Calendar c = Calendar.getInstance();
c.setTime(parse(date, format));
long t1 = c.getTime().getTime();
return (int)(t/1000 - t1/1000)/3600/24;
}
}