When archiving to datetree:
(setq org-archive-location "file.ext::datetree/")

The following produces unexpected result on "Minimal Example":
1. Archive first TODO "A1".

2. Archive second TODO "A2".


* Minimal Example
** DONE A1
   CLOSED: [2016-06-28 Tue 21:00]

** DONE A2
   CLOSED: [2016-06-14 Tue 21:00]


Result (no day headline for 2016-06-14):
* 2016
** 2016-06 June
**** DONE A2
     CLOSED: [2016-06-14 Tue 21:00]

*** 2016-06-28 Tuesday
**** DONE A1
     CLOSED: [2016-06-28 Tue 21:00]


Expected Result:
* 2016
** 2016-06 June
*** 2016-06-14 Tuesday
**** DONE A2
     CLOSED: [2016-06-14 Tue 21:00]

*** 2016-06-28 Tuesday
**** DONE A1
     CLOSED: [2016-06-28 Tue 21:00]


Emacs  : GNU Emacs 25.1.1 (x86_64-w64-mingw32)
 of 2016-09-22
Package: Org-mode version 8.3.6 (8.3.6-6-g194e51-elpa @
.emacs.d/elpa/org-20161003/)

current state:
==============
(setq
 org-tab-first-hook '(org-hide-block-toggle-maybe
org-babel-hide-result-toggle-maybe org-babel-header-arg-expand)
 org-speed-command-hook '(org-speed-command-default-hook
org-babel-speed-command-hook)
 org-occur-hook '(org-first-headline-recenter)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-confirm-shell-link-function 'yes-or-no-p
 org-after-todo-state-change-hook '(org-clock-out-if-current)
 org-src-mode-hook '(org-src-babel-configure-edit-buffer
org-src-mode-configure-edit-buffer)
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-babel-pre-tangle-hook '(save-buffer)
 org-mode-hook '(#[nil "\300\301\302\303\304$\207"
           [org-add-hook change-major-mode-hook org-show-block-all append
local] 5]
         #[nil "\300\301\302\303\304$\207"
           [org-add-hook change-major-mode-hook org-babel-show-result-all
append local] 5]
         org-babel-result-hide-spec org-babel-hide-all-hashes)
 org-archive-hook '(org-attach-archive-delete-maybe)
 org-ctrl-c-ctrl-c-hook '(org-babel-hash-at-point
org-babel-execute-safely-maybe)
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
org-cycle-show-empty-lines
          org-optimize-window-after-visibility-change)
 org-archive-location "archive.arc::datetree/"
 org-confirm-elisp-link-function 'yes-or-no-p
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 )