public String getMonday(String date) { if (date == null || date.equals("")) { System.out.println("date is null or empty"); return "0000-00-00 00:00:00"; } SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); Date d = null; try { d = format.parse(date); } catch(Exception e) { e.printStackTrace(); } Calendar cal = Calendar.getInstance(); cal.setTime(d); //set the first day of the week is Monday cal.setFirstDayOfWeek(Calendar.MONDAY); cal.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY); return format.format(cal.getTime())+ " 00:00:00"; }