Hi all,
I'm new to using org-mode for time tracking, and have run into an odd issue
with using "day" steps where the date is getting offset sometimes.

I saw the issue with 26.1, was not fixed by updating  to current
environment with an empty init.el on OS X:
Emacs  : GNU Emacs 26.3 (build 1, x86_64-apple-darwin18.2.0, NS
appkit-1671.20 Version 10.14.3 (Build 18D109))
 of 2019-09-02
Package: Org mode version 9.1.9 (release_9.1.9-65-g5e4542 @
/Applications/Emacs.app/Contents/Resources/lisp/org/)

current state:
==============
(setq
 org-src-mode-hook '(org-src-babel-configure-edit-buffer
    org-src-mode-configure-edit-buffer)
 org-after-todo-state-change-hook '(org-clock-out-if-current)
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-mode-hook '(#[0 "\300\301\302\303\304$\207"
  [add-hook change-major-mode-hook org-show-block-all append
   local]
  5]
#[0 "\300\301\302\303\304$\207"
  [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-confirm-elisp-link-function 'yes-or-no-p
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-bibtex-headline-format-function #[257 "\300 \236A\207" [:title] 3
"\n\n(fn ENTRY)"]
 org-babel-pre-tangle-hook '(save-buffer)
 org-tab-first-hook '(org-babel-hide-result-toggle-maybe
     org-babel-header-arg-expand)
 org-occur-hook '(org-first-headline-recenter)
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
 org-cycle-show-empty-lines
 org-optimize-window-after-visibility-change)
 org-speed-command-hook '(org-speed-command-activate
 org-babel-speed-command-activate)
 org-confirm-shell-link-function 'yes-or-no-p
 org-link-parameters '(("id" :follow org-id-open)
      ("rmail" :follow org-rmail-open :store
org-rmail-store-link)
      ("mhe" :follow org-mhe-open :store org-mhe-store-link)
      ("irc" :follow org-irc-visit :store org-irc-store-link)
      ("info" :follow org-info-open :export org-info-export
:store org-info-store-link)
      ("gnus" :follow org-gnus-open :store
org-gnus-store-link)
      ("docview" :follow org-docview-open :export
org-docview-export :store org-docview-store-link)
      ("bibtex" :follow org-bibtex-open :store
org-bibtex-store-link)
      ("bbdb" :follow org-bbdb-open :export org-bbdb-export
:complete org-bbdb-complete-link :store
org-bbdb-store-link)
      ("w3m" :store org-w3m-store-link) ("file+sys")
      ("file+emacs") ("doi" :follow org--open-doi-link)
      ("elisp" :follow org--open-elisp-link)
      ("file" :complete org-file-complete-link)
      ("ftp" :follow
(lambda (path) (browse-url (concat "ftp:" path))))
      ("help" :follow org--open-help-link)
      ("http" :follow
(lambda (path) (browse-url (concat "http:" path))))
      ("https" :follow
(lambda (path) (browse-url (concat "https:" path))))
      ("mailto" :follow
(lambda (path) (browse-url (concat "mailto:" path))))
      ("news" :follow
(lambda (path) (browse-url (concat "news:" path))))
      ("shell" :follow org--open-shell-link))
 )


Below  is a simple org file which demonstrates the problem.   The aggregate
numbers are correct for the file, but when I make a clocktable stepping by
day, the [2019-11-03 Sun] entry is repeated and every date after that is
off by one.  Using stepskip0 doesn't change that .

---

* Day 1
  :LOGBOOK:
  CLOCK: [2019-11-01 Fri 10:00]--[2019-11-01 Fri 11:00] =>  1:00
  :END:
* Day 2
  :LOGBOOK:
  CLOCK: [2019-11-02 Sat 10:00]--[2019-11-02 Sat 12:00] =>  2:00
  :END:
* Day 3
  :LOGBOOK:
  CLOCK: [2019-11-03 Sun 10:00]--[2019-11-03 Sun 13:00] =>  3:00
  :END:
* Day 4
  :LOGBOOK:
  CLOCK: [2019-11-04 Mon 10:00]--[2019-11-04 Mon 14:00] =>  4:00
  :END:
* Day 5
  :LOGBOOK:
  CLOCK: [2019-11-05 Tue 10:00]--[2019-11-05 Tue 15:00] =>  5:00
  :END:
* Day 6
  :LOGBOOK:
  CLOCK: [2019-11-06 Wed 10:00]--[2019-11-06 Wed 16:00] =>  6:00
  :END:

#+BEGIN: clocktable :scope file :maxlevel 2
#+CAPTION: Clock summary at [2019-11-27 Wed 16:41]
| Headline     |    Time |
|--------------+---------|
| *Total time* | *21:00* |
|--------------+---------|
| Day 1        |    1:00 |
| Day 2        |    2:00 |
| Day 3        |    3:00 |
| Day 4        |    4:00 |
| Day 5        |    5:00 |
| Day 6        |    6:00 |
#+END:


#+BEGIN: clocktable :scope file :maxlevel 2 :block thismonth :step day
:stepskip0 t

Daily report: [2019-11-01 Fri]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *1:00* |
|--------------+--------|
| Day 1        | 1:00   |

Daily report: [2019-11-02 Sat]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *2:00* |
|--------------+--------|
| Day 2        | 2:00   |

Daily report: [2019-11-03 Sun]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *3:00* |
|--------------+--------|
| Day 3        | 3:00   |

Daily report: [2019-11-03 Sun]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *4:00* |
|--------------+--------|
| Day 4        | 4:00   |

Daily report: [2019-11-04 Mon]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *5:00* |
|--------------+--------|
| Day 5        | 5:00   |

Daily report: [2019-11-05 Tue]
| Headline     | Time   |
|--------------+--------|
| *Total time* | *6:00* |
|--------------+--------|
| Day 6        | 6:00   |

#+END: