make timestamps the same on every file

Author: moritz

htmlify.pl

@@ -432,10 +432,11 @@ (Bool :$debug, Bool :$typegraph = False)
 }
 
 sub footer-html() {
+    state $dt = ~DateTime.now;
     qq[
     <div id="footer">
         <p>
-            Generated on {DateTime.now} from the sources at
+            Generated on $dt from the sources at
             <a href="https://github.com/perl6/doc">perl6/doc on github</a>.
         </p>
         <p>