diff --git a/preface.tex b/preface.tex
index 64d9d40..b510ac1 100644
--- a/preface.tex
+++ b/preface.tex
@@ -28,6 +28,6 @@ You can always send feedback on the book to
 \texttt{ahslaaks@cs.helsinki.fi}.
 
 \begin{flushright}
-Helsinki, October 2017 \\
+Helsinki, July 2018 \\
 Antti Laaksonen
 \end{flushright}