Originally Posted by gmayor

Which 'document property' did you have in mind?
Your message subject says 'date field'. If you want to insert a date field, you don't need a macro you simply insert a date field with a formatting switch to dsiplay only the year e.g. { DATE \@ "yyyy" } - use CTRL+F9 for the field brackets. The rest is just text thus
3/31/{ DATE \@ "yyyy" }
will always show the last day of March in the current year.