You have cross-posted. Your link is not to the source of your field or your research, but to you asking the same question in another forum. This is apparently the third forum in which you have posted. Birthdate would refer to a bookmark named birthdate that would contain the date. That could be a bookmark around a date picker content control.

It is time for you to start learning to deal with field code. Period. You want to do something that requires a complex field, it is time to learn at least how to create, edit, and manipulate fields.

Here are directions you can follow to do that.

• Dealing with Fields in Microsoft Word

Here is a tutorial document with field codes for all sorts of calculations based upon dates, including the one you seek. Read the introductory material before finding the field you need. You can then find that field and copy it into your document/template. It is pinned at the top of this forum.

• Microsoft Word Date Calculation Tutorial

MVP Paul Edstein has done all the heavy lifting, but you are required to think. If you do not understand how a bookmark is created someone here will be happy to help you with that. I do not certify that you have a working field already. You seem to think it should work.

Here you can find a utility that can take text like that you have posted and convert it to a working field.

• Convert Fields to Text and Vice Versa by Word MVP Graham Mayor