Java Utililty Methods Day of

Calendar c = Calendar.getInstance();
c.add(Calendar.YEAR, -Integer.parseInt(age));
SimpleDateFormat format = new SimpleDateFormat(defaultDatePattern);
return format.format(c.getTime());

String birthDay;
if (idCard.length() == 15) {
    birthDay = "19" + idCard.substring(6, 12);
} else {
    birthDay = idCard.substring(6, 14);
SimpleDateFormat dateFormat = new SimpleDateFormat(DateFormatPattern, Locale.ENGLISH);
return dateFormat.parse(birthDay);
...

return getFormat("MM-dd");

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
return sdf.format(date);

Date now = new Date();
return yyyyMmDd.format(new Date(now.getTime() - (long) days * 24 * 60 * 60 * 1000));

Calendar calendar = Calendar.getInstance();
Date date = yyyyMMddFormat.parse(dayStr);
calendar.setTime(date);
return calendar;

try {
    SimpleDateFormat sf = new SimpleDateFormat("yyyyMMddHHmmss");
    return sf.parse(sf.format(currentDate)).getTime() / 1000;
} catch (Exception e) {
    e.printStackTrace();
return -1;

Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
return new SimpleDateFormat("yyyy-MM-dd 00:00:00").format(calendar.getTime());

String dateText = getDayText(day);
File tableDir = new File(logDir, Integer.toString(tableId));
File datafile = new File(tableDir, dateText + ".dat");
return datafile;

Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, dayNum);
return cal.getTime();