Change a date from invalid to valid.

Jan 1, 1990 was actually a Monday.

Change-Id: I4af872e699c590973a35595cb866d768fd9ed808
diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/WebServer.java b/dev/codeserver/java/com/google/gwt/dev/codeserver/WebServer.java
index cad1d4f..9e16f64 100644
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/WebServer.java
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/WebServer.java
@@ -90,7 +90,7 @@
 
   private static final MimeTypes MIME_TYPES = new MimeTypes();
 
-  private static final String TIME_IN_THE_PAST = "Fri, 01 Jan 1990 00:00:00 GMT";
+  private static final String TIME_IN_THE_PAST = "Mon, 01 Jan 1990 00:00:00 GMT";
 
   private final SourceHandler sourceHandler;
   private final SymbolMapHandler symbolMapHandler;