Java simple date format

SimpleDateFormat

new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(request.getParameter("issued_date"))

get seconds

long milliseconds = date.getTime();
Long seconds = milliseconds / 1000L;

set seconds

long milliseconds = longDate * 1000L;
Date date = new Date(milliseconds);

Calendar

Calendar calendar = Calendar.getInstance();

or init from date

Calendar calendar= DateUtils.toCalendar(date);

Set diff : i.e. Plus one day

calendar.add(Calendar.DAY_OF_YEAR, 1);

Set

calendar.set(Calendar.HOUR_OF_DAY, 0);

get time

calendar.getTime()

calendar.get

cal.get(Calendar.ERA)

Calendar.YEAR, Calendar.DAY_OF_YEAR