Random generate a date which is after the date in string format

I got a question regarding the random generated date. So what I am trying to do is I random generate a day between 1-30, month between 1-12 and year by default is 2016.

Random rand = new Random();
        int date = 1 + rand.nextInt((30 - 1) + 1);
        int month = 1 + rand.nextInt((12 - 1) + 1);
        if(month == 1){
            monthStr = "January";
        }else if(month == 2){
            monthStr = "February";
        }else if(month == 3){
            monthStr = "March";
        }else if(month == 4){
            monthStr = "April";
        }else if(month == 5){
            monthStr = "May";
        }else if(month == 6){
            monthStr = "June";
        }else if(month == 7){
            monthStr = "July";
        }else if(month == 8){
            monthStr = "August";
        }else if(month == 9){
            monthStr = "September";
        }else if(month == 10){
            monthStr = "October";
        }else if(month == 11){
            monthStr = "November";
        }else if(month == 12){
            monthStr = "December";
        }

I used a for loop to random generate the date for 100 times. Then, I append the string together to store it into a string array list.

ArrayList<String> dateTimeList = new ArrayList<String>();
dateTimeList.add(date + " " +  monthStr + " 2016");

After that, I pass the entire list into another method. In this method, I am trying to generate again random date but in this case, I need to generate a date which is after the above one.

In another word, the first time when I random generated 100 dates is for the filing date. Then I pass in the entire list into another method, inside that method, I need to generate another 100 dates which is after each filing date.

Any ideas how could I achieve this? I know there is some other way to generate a random date but I preferred to be in this way as I will be using it in some other places.

Thanks in advance.