You should read these tutorials:
Basically, the process is to use a custom calculation script to read the entered date string, convert it to a Date object (using the util.scand method), add X days to it (using the setDate method) and then print out the new date (using the util.printd method).
If you're interested in a tool that will allow you to easily set it up without having to write any code, check out this one I've developed exactly for this purpose a while ago: Custom-made Adobe Scripts: Acrobat -- Apply Automatic Date Calculation
This has been asked many times in many variations as to the number of days to populate. You can search for the questions to see many scripts. You will need to change the name of the fields to work with your form. This is a form where preplanning fiend names can big difference in how much coding needs to be done. With careful field naming, one can reduce much of the scripting to only a few lines in a loop to process all 14 dqys.
Ohh thank you, yes in the ref, it was milliseconds and showing the time, I just need dates. Thanks for point me in the right direction.
No matter how you compute the dates, you need to use the util.prind method to create the formatted date or time string. You also need to know that the format time options only allow values for valid times occurring within one day. This means you can not use the time format for a field that will have an elapsed time of 24 hours or more.