My mistake. I repasted in Custom Calculation Script and it still did not work. I noticed that in your code, you formatted the date with 2 digits for day, month and 4 digits for year. So I changed my DOB text field to 2 digits for day and month and 4 digits for year. Do those need to be the same?
It still did not work, and then I noticed in your code that you have day first, then month, then year. So I edited the code and put mm/dd/yyy in place of dd/mm/yyyy. I retried and now my new Age text field populates an age when a date of birth is entered into the DOB field. But unfortunately, it was the wrong age! 
I entered 03/28/1983 into the DOB field and the Age field populated 29, instead of 30. Any thoughts why?