diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index ef00dc73f91..b021c4d704c 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -676,8 +676,8 @@ A and B are the time values to compare."
            (side-effect-free t))
   (unless (time-equal-p a b)
     `(different-time-values
-      ,(format-time-string "%F %T.%N %Z" a t)
-      ,(format-time-string "%F %T.%N %Z" b t)
+      ,(format-time-string "%F %T.%N%z" a t)
+      ,(format-time-string "%F %T.%N%z" b t)
       difference
       ,(format-time-string "%s.%N" (time-subtract a b) t))))
 (function-put #'time-equal-p 'ert-explainer #'ert--explain-time-equal-p)
diff --git a/test/lisp/emacs-lisp/ert-tests.el b/test/lisp/emacs-lisp/ert-tests.el
index 7a08cb47d82..0ce531386c8 100644
--- a/test/lisp/emacs-lisp/ert-tests.el
+++ b/test/lisp/emacs-lisp/ert-tests.el
@@ -796,8 +796,8 @@ This macro is used to test if macroexpansion in `should' works."
   (should-not (ert--explain-time-equal-p 123 '(0 123 0 0)))
   (should (equal (ert--explain-time-equal-p 123 '(0 120 0 0))
                  '(different-time-values
-                   "1970-01-01 00:02:03.000000000 UTC"
-                   "1970-01-01 00:02:00.000000000 UTC"
+                   "1970-01-01 00:02:03.000000000+0000"
+                   "1970-01-01 00:02:00.000000000+0000"
                    difference "3.000000000"))))
 
 (ert-deftest ert-test-stats-set-test-and-result ()