plk#595 - doc clarification and loc strings update

doc/latex/biblatex/biblatex.tex

@@ -980,9 +980,11 @@ \subsubsection{Data Fields}
 
 An annex to the \bibfield{maintitle}, to be printed in a different font.
 
-\fielditem{month}{datepart}
+\fielditem{month}{literal}
 
-The publication month. This must be an integer, not an ordinal or a string. Don't say |month={January}| but |month={1}|. The bibliography style converts this to a language dependent string or ordinal where required. See also \bibfield{date} as well as \secref{bib:use:iss, bib:use:dat}.
+The publication month. This must be an integer, not an ordinal or a string. Don't say |month={January}| but |month={1}|. The bibliography style converts this to a language dependent string or ordinal where required. This field is a literal field only when given
+explicitly in the data (for plain \bibtex compatibility for example). It is
+however better to use the \bibfield{date} field as this supports many more features. See \secref{bib:use:dat}.
 
 \fielditem{nameaddon}{literal}
 
@@ -1126,7 +1128,10 @@ \subsubsection{Data Fields}
 
 \fielditem{year}{literal}
 
-The year of publication. It is better to use the \bibfield{date} field as this is compatible with plain years too. See \secref{bib:use:dat}.
+The year of publication. This field is a literal field only when given
+explicitly in the data (for plain \bibtex compatibility for example). It is
+however better to use the \bibfield{date} field as this is compatible with
+plain years too and supports many more features. See \secref{bib:use:dat}.
 
 \end{fieldlist}