Install A Date Selector Widget

If you're using an older version and/or if you need a Date picker with more options: https://www.abracadabrapdf.net/utilitaires/utilities-in-english/acrobat-utilities/magicdate-picker/

If you use a relatively new version of Acrobat/Reader you can just set a text field's Format to Date and a calendar picker will appear automatically. No scripts required.