RandomShiftOnDate.java

    public static Date randomShiftOnDate(Date someDate) {
        Random random = new Random();
        int randomValue = random.nextInt(31) * 60 * 1000; // 30 min.
        boolean subtract = random.nextBoolean();
        if (subtract) randomValue *= -1;
        
        long time = someDate.getTime();
        time += randomValue;
        
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(time);
        return cal.getTime();
    }