diff --git a/t/lib-t6000.sh b/t/lib-t6000.sh
index e2c361563b..4ffd90127e 100644
--- a/t/lib-t6000.sh
+++ b/t/lib-t6000.sh
@@ -82,6 +82,14 @@ on_committer_date () {
 	"$@"
 }
 
+on_dates () {
+	assign_fake_date GIT_COMMITTER_DATE "$1"
+	assign_fake_date GIT_AUTHOR_DATE "$2"
+	export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
+	shift 2
+	"$@"
+}
+
 # Execute a command and suppress any error output.
 hide_error () {
 	"$@" 2>/dev/null
diff --git a/t/t6003-rev-list-topo-order.sh b/t/t6003-rev-list-topo-order.sh
index 0e3b7e1ea3..77bf2ca1e1 100755
--- a/t/t6003-rev-list-topo-order.sh
+++ b/t/t6003-rev-list-topo-order.sh
@@ -16,32 +16,32 @@ list_duplicates()
 date >path0
 git update-index --add path0
 save_tag tree git write-tree
-on_committer_date "00:00" hide_error save_tag root unique_commit root tree
-on_committer_date "00:01" save_tag l0 unique_commit l0 tree -p root
-on_committer_date "00:02" save_tag l1 unique_commit l1 tree -p l0
-on_committer_date "00:03" save_tag l2 unique_commit l2 tree -p l1
-on_committer_date "00:04" save_tag a0 unique_commit a0 tree -p l2
-on_committer_date "00:05" save_tag a1 unique_commit a1 tree -p a0
-on_committer_date "00:06" save_tag b1 unique_commit b1 tree -p a0
-on_committer_date "00:07" save_tag c1 unique_commit c1 tree -p b1
-on_committer_date "00:08" as_author foobar@example.com save_tag b2 unique_commit b2 tree -p b1
-on_committer_date "00:09" save_tag b3 unique_commit b3 tree -p b2
-on_committer_date "00:10" save_tag c2 unique_commit c2 tree -p c1 -p b2
-on_committer_date "00:11" save_tag c3 unique_commit c3 tree -p c2
-on_committer_date "00:12" save_tag a2 unique_commit a2 tree -p a1
-on_committer_date "00:13" save_tag a3 unique_commit a3 tree -p a2
-on_committer_date "00:14" save_tag b4 unique_commit b4 tree -p b3 -p a3
-on_committer_date "00:15" save_tag a4 unique_commit a4 tree -p a3 -p b4 -p c3
-on_committer_date "00:16" save_tag l3 unique_commit l3 tree -p a4
-on_committer_date "00:17" save_tag l4 unique_commit l4 tree -p l3
-on_committer_date "00:18" save_tag l5 unique_commit l5 tree -p l4
-on_committer_date "00:19" save_tag m1 unique_commit m1 tree -p a4 -p c3
-on_committer_date "00:20" save_tag m2 unique_commit m2 tree -p c3 -p a4
-on_committer_date "00:21" hide_error save_tag alt_root unique_commit alt_root tree
-on_committer_date "00:22" save_tag r0 unique_commit r0 tree -p alt_root
-on_committer_date "00:23" save_tag r1 unique_commit r1 tree -p r0
-on_committer_date "00:24" save_tag l5r1 unique_commit l5r1 tree -p l5 -p r1
-on_committer_date "00:25" save_tag r1l5 unique_commit r1l5 tree -p r1 -p l5
+on_dates "00:00" "00:00" hide_error save_tag root unique_commit root tree
+on_dates "00:01" "00:01" save_tag l0 unique_commit l0 tree -p root
+on_dates "00:02" "00:02" save_tag l1 unique_commit l1 tree -p l0
+on_dates "00:03" "00:03" save_tag l2 unique_commit l2 tree -p l1
+on_dates "00:04" "00:04" save_tag a0 unique_commit a0 tree -p l2
+on_dates "00:05" "00:05" save_tag a1 unique_commit a1 tree -p a0
+on_dates "00:06" "00:06" save_tag b1 unique_commit b1 tree -p a0
+on_dates "00:07" "00:07" save_tag c1 unique_commit c1 tree -p b1
+on_dates "00:08" "00:08" as_author foobar@example.com save_tag b2 unique_commit b2 tree -p b1
+on_dates "00:09" "00:09" save_tag b3 unique_commit b3 tree -p b2
+on_dates "00:10" "00:10" save_tag c2 unique_commit c2 tree -p c1 -p b2
+on_dates "00:11" "00:11" save_tag c3 unique_commit c3 tree -p c2
+on_dates "00:12" "00:12" save_tag a2 unique_commit a2 tree -p a1
+on_dates "00:13" "00:13" save_tag a3 unique_commit a3 tree -p a2
+on_dates "00:14" "00:14" save_tag b4 unique_commit b4 tree -p b3 -p a3
+on_dates "00:15" "00:15" save_tag a4 unique_commit a4 tree -p a3 -p b4 -p c3
+on_dates "00:16" "00:16" save_tag l3 unique_commit l3 tree -p a4
+on_dates "00:17" "00:17" save_tag l4 unique_commit l4 tree -p l3
+on_dates "00:18" "00:18" save_tag l5 unique_commit l5 tree -p l4
+on_dates "00:19" "00:19" save_tag m1 unique_commit m1 tree -p a4 -p c3
+on_dates "00:20" "00:20" save_tag m2 unique_commit m2 tree -p c3 -p a4
+on_dates "00:21" "00:21" hide_error save_tag alt_root unique_commit alt_root tree
+on_dates "00:22" "00:22" save_tag r0 unique_commit r0 tree -p alt_root
+on_dates "00:23" "00:23" save_tag r1 unique_commit r1 tree -p r0
+on_dates "00:24" "00:24" save_tag l5r1 unique_commit l5r1 tree -p l5 -p r1
+on_dates "00:25" "00:25" save_tag r1l5 unique_commit r1l5 tree -p r1 -p l5
 
 
 hide_error save_tag e1 as_author e@example.com unique_commit e1 tree