Code Cleanup

- Remove the code related to the format "day of year" (number of day starting
  from the January 1) as mktime does not allow to specify it with the field
  tm_yday.
- Cleaner check of the date (everything is done by Date::valid).
- Correct hour, minute and second is also checked.

test/date.t.cpp

@@ -35,7 +35,7 @@ Context context;
 ////////////////////////////////////////////////////////////////////////////////
 int main (int argc, char** argv)
 {
-  UnitTest t (177);
+  UnitTest t (179);
 
   try
   {
@@ -86,6 +86,9 @@ int main (int argc, char** argv)
     t.ok    (Date::valid ("2/29/2008"), "valid: 2/29/2008");
     t.notok (Date::valid ("2/29/2007"), "invalid: 2/29/2007");
 
+    t.ok    (Date::valid (366, 2008), "valid: 366 days in 2008");
+    t.notok (Date::valid (366, 2007), "invalid: 366 days in 2007");
+
     // Time validity.
     t.ok    (Date::valid (2, 28, 2010,  0,  0,  0), "valid 2/28/2010 0:00:00");
     t.ok    (Date::valid (2, 28, 2010, 23, 59, 59), "valid 2/28/2010 23:59:59");