bug#4065: 23.1.50; org includes calendar entries on the wrong day

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

This only happens for the first time running org-agenda in a fresh emacs
session.

Settings to reproduce the bug with Emacs -q:

(define-key mode-specific-map [?a] 'org-agenda)
(define-key mode-specific-map [?l] 'org-store-link)
(setq org-agenda-include-diary t)

(setq calendar-date-style 'european)
(setq diary-number-of-entries 7)
(add-hook 'diary-hook 'appt-make-list)

Add an entry to the diary file such as:

    8 Aug 2009 Test2

--------------------------------
Week-agenda (W32):
Monday      3 August 2009 W32
  Diary:      Test2
  Diary:      
  Diary:      Thursday, 6 August 2009
  Diary:      =======================
Tuesday     4 August 2009
Wednesday   5 August 2009
Thursday    6 August 2009
Friday      7 August 2009
Saturday    8 August 2009
  Diary:      Test2
Sunday      9 August 2009
--------------------------------

Running org-agend a second time does not have this problem. This also
happens in org 6.21b.