#6 Use biblatex default "no date" abbreviation for bib entries without date

config/config.tex

@@ -105,6 +105,12 @@
     uniquelist=false
 ]{biblatex}
 \bibliography{library/library}
+\DeclareLabeldate{
+  \field{date}
+  \field{eventdate} 
+  \field{origdate}
+  \literal{nodate}
+}
 
 % Ebenentiefe der Nummerierung
 \setcounter{secnumdepth}{3}