diff --git a/site-lisp/timeline-tools-test.el b/site-lisp/timeline-tools-test.el
index dbe6d92..2de4ed6 100644
--- a/site-lisp/timeline-tools-test.el
+++ b/site-lisp/timeline-tools-test.el
@@ -202,8 +202,9 @@ CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
 
 (ert-deftest timeline-tools-test-clockline-no-conflict-1 ()
   "Test `timeline-tools-clockline-no-conflict’ with complex example."
-  (with-temp-buffer
-    (insert "
+  (let ((system-time-locale "C"))
+    (with-temp-buffer
+      (insert "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-07 Sun 13:15]--[2018-01-07 Sun 14:00] => 0:45
@@ -233,13 +234,14 @@ CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
 * Task 2
 :LOGBOOK:
 :END:
-"))))
+")))))
 
 (ert-deftest timeline-tools-test-add-clockline-to-marker-1 ()
   "Test `timeline-tools-add-clockline-to-marker’ without running
 clock."
-  (with-temp-buffer
-    (insert "
+  (let ((system-time-locale "C"))
+    (with-temp-buffer
+      (insert "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-07 Sun 13:15]--[2018-01-07 Sun 14:00] => 0:45
@@ -253,16 +255,16 @@ CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
 CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
 :END:
 ")
-    (org-mode)
-    (goto-char 216)
-    (let ((result (timeline-tools-add-clockline-to-marker
-                   (point-marker)
-                   (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
-                   (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+      (org-mode)
+      (goto-char 216)
+      (let ((result (timeline-tools-add-clockline-to-marker
+                     (point-marker)
+                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
 
-      (should (null result))
-      (should (equal (buffer-string)
-                     "
+        (should (null result))
+        (should (equal (buffer-string)
+                       "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
@@ -272,13 +274,14 @@ CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
 :LOGBOOK:
 CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
 :END:
-")))))
+"))))))
 
 (ert-deftest timeline-tools-test-add-clockline-to-marker-2 ()
   "Test `timeline-tools-add-clockline-to-marker’ with running
 clock at same task."
-  (with-temp-buffer
-    (insert "
+  (let ((system-time-locale "C"))
+    (with-temp-buffer
+      (insert "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-10 Wed 10:07]--[2018-01-12 Fri 14:00] => 51:53
@@ -293,22 +296,22 @@ CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
 CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
 :END:
 ")
-    (org-mode)
-    (let (;; simulate running clock at Task 2
-          (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
-          (org-clock-marker (progn (goto-char 264) (point-marker)))
-          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
-      (let ((result (timeline-tools-add-clockline-to-marker
-                     org-clock-hd-marker
-                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
-                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+      (org-mode)
+      (let (;; simulate running clock at Task 2
+            (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
+            (org-clock-marker (progn (goto-char 264) (point-marker)))
+            (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+        (let ((result (timeline-tools-add-clockline-to-marker
+                       org-clock-hd-marker
+                       (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                       (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
 
-        (should (null result))
-        (should (equal org-clock-start-time
-                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
-                               '(0 0))))
-        (should (equal (buffer-string)
-                       "
+          (should (null result))
+          (should (equal org-clock-start-time
+                         (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                                 '(0 0))))
+          (should (equal (buffer-string)
+                         "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
@@ -319,13 +322,14 @@ CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
 CLOCK: [2018-01-11 Thu 13:33]
 CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
 :END:
-"))))))
+")))))))
 
 (ert-deftest timeline-tools-test-add-clockline-to-marker-3 ()
   "Test `timeline-tools-add-clockline-to-marker’ with running
 clock at same task."
-  (with-temp-buffer
-    (insert "
+  (let ((system-time-locale "C"))
+    (with-temp-buffer
+      (insert "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-08 Mon 16:15]--[2018-01-10 Wed 13:10] => 44:55
@@ -339,22 +343,22 @@ CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
 CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
 :END:
 ")
-    (org-mode)
-    (let (;; simulate running clock at Task 2
-          (org-clock-hd-marker (progn (goto-char 153) (point-marker)))
-          (org-clock-marker (progn (goto-char 201) (point-marker)))
-          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
-      (let ((result (timeline-tools-add-clockline-to-marker
-                     (progn (goto-char 2) (point-marker))
-                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
-                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+      (org-mode)
+      (let (;; simulate running clock at Task 2
+            (org-clock-hd-marker (progn (goto-char 153) (point-marker)))
+            (org-clock-marker (progn (goto-char 201) (point-marker)))
+            (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+        (let ((result (timeline-tools-add-clockline-to-marker
+                       (progn (goto-char 2) (point-marker))
+                       (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                       (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
 
-        (should (null result))
-        (should (equal org-clock-start-time
-                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
-                               '(0 0))))
-        (should (equal (buffer-string)
-                       "
+          (should (null result))
+          (should (equal org-clock-start-time
+                         (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                                 '(0 0))))
+          (should (equal (buffer-string)
+                         "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
@@ -364,14 +368,15 @@ CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
 :LOGBOOK:
 CLOCK: [2018-01-11 Thu 13:33]
 :END:
-"))))))
+")))))))
 
 (ert-deftest timeline-tools-test-add-clockline-to-marker-4 ()
   "Test `timeline-tools-add-clockline-to-marker’ with running
 clock at other task, and where afterwards only the running clock
 line is left."
-  (with-temp-buffer
-    (insert "
+  (let ((system-time-locale "C"))
+    (with-temp-buffer
+      (insert "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-10 Wed 10:07]--[2018-01-12 Fri 14:00] => 51:53
@@ -386,22 +391,22 @@ CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
 CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
 :END:
 ")
-    (org-mode)
-    (let (;; simulate running clock at Task 2
-          (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
-          (org-clock-marker (progn (goto-char 264) (point-marker)))
-          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
-      (let ((result (timeline-tools-add-clockline-to-marker
-                     (progn (goto-char 2) (point-marker))
-                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
-                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+      (org-mode)
+      (let (;; simulate running clock at Task 2
+            (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
+            (org-clock-marker (progn (goto-char 264) (point-marker)))
+            (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+        (let ((result (timeline-tools-add-clockline-to-marker
+                       (progn (goto-char 2) (point-marker))
+                       (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                       (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
 
-        (should (null result))
-        (should (equal org-clock-start-time
-                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
-                               '(0 0))))
-        (should (equal (buffer-string)
-                       "
+          (should (null result))
+          (should (equal org-clock-start-time
+                         (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                                 '(0 0))))
+          (should (equal (buffer-string)
+                         "
 * Task 1
 :LOGBOOK:
 CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
@@ -412,6 +417,6 @@ CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
 :LOGBOOK:
 CLOCK: [2018-01-11 Thu 13:33]
 :END:
-"))))))
+")))))))
 
 ;;; timeline-tools-test.el ends here