Java Utililty Methods Day of

SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DAY_OF_YEAR, deltaDay);
return format.format(cal.getTime());

List<String> list = new ArrayList<String>();
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
Date getDate = sdf.parse(date);
GregorianCalendar gc = new GregorianCalendar();
gc.setTime(getDate);
for (int i = 0; i < afterDays; i++) {
    gc.add(Calendar.DATE, 1);
    getDate = gc.getTime();
...

Calendar cal = Calendar.getInstance();
if (cal.before(birthDay)) {
    throw new IllegalArgumentException("The birthDay is before Now.It's unbelievable!");
int yearNow = cal.get(Calendar.YEAR);
int monthNow = cal.get(Calendar.MONTH);
int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
cal.setTime(birthDay);
...

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Date birthDay = df.parse(birthDayString);
Calendar cal = Calendar.getInstance();
int yearNow = cal.get(Calendar.YEAR);
int monthNow = cal.get(Calendar.MONTH);
int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
cal.setTime(birthDay);
int yearBirth = cal.get(Calendar.YEAR);
...

int day = Integer.parseInt(dob.substring(0, 2));
String month = dob.substring(2, 5);
int mon = 1;
switch (month) {
case "JAN":
    mon = 1;
    break;
case "FEB":
...

Calendar cl = Calendar.getInstance();
Long clTemp = cl.getTimeInMillis() - day * 24 * 60 * 60 * 1000L;
cl.setTimeInMillis(clTemp);
return getFormatDate(cl.getTime(), "yyyy-MM-dd");

Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.DAY_OF_MONTH, days);
SimpleDateFormat df = new SimpleDateFormat(format);
return df.format(calendar.getTime());

Date begin, end;
begin = day;
Calendar cal = getCalendar();
cal.setTime(begin);
cal.set(Calendar.HOUR, 23);
cal.add(Calendar.MINUTE, 59);
cal.add(Calendar.SECOND, 59);
cal.set(Calendar.MILLISECOND, 999);
...

String beginDay = new SimpleDateFormat(EARER_IN_THE_DAY).format(date);
try {
    return parserStringToDate(beginDay, LONG_DATE_FORMAT_STR);
} catch (ParseException e) {
return null;

Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.DAY_OF_YEAR, offset);
date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
return Long.valueOf(dateFormat.format(date) + "0000");