New Post: Creating date fields in a new source

I want to congratulate you, Yves. For the great job on Bibword. Thank you very much! It's a wonderfull job!

And my question is that I was creating a new source and I needed three date fields (one new in addition to the default fields). I got to create the code as requested (with the words year, month and day in front), however one of the fields simply does not appear. What should I change to make it work?

Thanks for the help in advance!