FormRouter offers a very nice add-on feature for Acrobat: A calendar widget. However, this widget only contains English texts, and sometimes there's a need to localize those texts to other languages.
To do that I've developed this tool that allows you to edit the FR calendar widgets in your file and apply any texts you want to the day and month fields in them.

Here we have a PDF file in Portuguese with a FR widget added to it. As you can see, the texts in the calendar are in English, which is not consistent with the rest of our file and doesn't look professional:

So we click on the "Localize FormRouter Calendars" button under Add-On Tools and enter the localized texts:

Now the calendar is edited to use the new texts, which looks much better, but its functionality remains exactly the same as before:

IMPORTANT: The script can not localize the date string that appears in the field after a selection is made in the calendar, only the calendar itself.