diff --git a/commit-graph.c b/commit-graph.c
index afc4f37442..123dbc7c21 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -753,15 +753,24 @@ static void fill_commit_graph_info(struct commit *item, struct commit_graph *g,
 	const unsigned char *commit_data;
 	struct commit_graph_data *graph_data;
 	uint32_t lex_index;
+	uint64_t date_high, date_low;
 
 	while (pos < g->num_commits_in_base)
 		g = g->base_graph;
 
+	if (pos >= g->num_commits + g->num_commits_in_base)
+		die(_("invalid commit position. commit-graph is likely corrupt"));
+
 	lex_index = pos - g->num_commits_in_base;
 	commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * lex_index;
 
 	graph_data = commit_graph_data_at(item);
 	graph_data->graph_pos = pos;
+
+	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
+	date_low = get_be32(commit_data + g->hash_len + 12);
+	item->date = (timestamp_t)((date_high << 32) | date_low);
+
 	graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 }
 
@@ -776,38 +785,22 @@ static int fill_commit_in_graph(struct repository *r,
 {
 	uint32_t edge_value;
 	uint32_t *parent_data_ptr;
-	uint64_t date_low, date_high;
 	struct commit_list **pptr;
-	struct commit_graph_data *graph_data;
 	const unsigned char *commit_data;
 	uint32_t lex_index;
 
 	while (pos < g->num_commits_in_base)
 		g = g->base_graph;
 
-	if (pos >= g->num_commits + g->num_commits_in_base)
-		die(_("invalid commit position. commit-graph is likely corrupt"));
+	fill_commit_graph_info(item, g, pos);
 
-	/*
-	 * Store the "full" position, but then use the
-	 * "local" position for the rest of the calculation.
-	 */
-	graph_data = commit_graph_data_at(item);
-	graph_data->graph_pos = pos;
 	lex_index = pos - g->num_commits_in_base;
-
 	commit_data = g->chunk_commit_data + (g->hash_len + 16) * lex_index;
 
 	item->object.parsed = 1;
 
 	set_commit_tree(item, NULL);
 
-	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
-	date_low = get_be32(commit_data + g->hash_len + 12);
-	item->date = (timestamp_t)((date_high << 32) | date_low);
-
-	graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
-
 	pptr = &item->parents;
 
 	edge_value = get_be32(commit_data + g->hash_len);
diff --git a/t/t5000-tar-tree.sh b/t/t5000-tar-tree.sh
index 3ebb0d3b65..7204799a0b 100755
--- a/t/t5000-tar-tree.sh
+++ b/t/t5000-tar-tree.sh
@@ -431,15 +431,33 @@ test_expect_success TAR_HUGE,LONG_IS_64BIT 'system tar can read our huge size' '
 	test_cmp expect actual
 '
 
-test_expect_success TIME_IS_64BIT 'set up repository with far-future commit' '
+test_expect_success TIME_IS_64BIT 'set up repository with far-future (2^34 - 1) commit' '
 	rm -f .git/index &&
-	echo content >file &&
+	echo foo >file &&
 	git add file &&
-	GIT_COMMITTER_DATE="@68719476737 +0000" \
+	GIT_COMMITTER_DATE="@17179869183 +0000" \
 		git commit -m "tempori parendum"
 '
 
-test_expect_success TIME_IS_64BIT 'generate tar with future mtime' '
+test_expect_success TIME_IS_64BIT 'generate tar with far-future mtime' '
+	git archive HEAD >future.tar
+'
+
+test_expect_success TAR_HUGE,TIME_IS_64BIT,TIME_T_IS_64BIT 'system tar can read our future mtime' '
+	echo 2514 >expect &&
+	tar_info future.tar | cut -d" " -f2 >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success TIME_IS_64BIT 'set up repository with far-far-future (2^36 + 1) commit' '
+	rm -f .git/index &&
+	echo content >file &&
+	git add file &&
+	GIT_TEST_COMMIT_GRAPH=0 GIT_COMMITTER_DATE="@68719476737 +0000" \
+		git commit -m "tempori parendum"
+'
+
+test_expect_success TIME_IS_64BIT 'generate tar with far-far-future mtime' '
 	git archive HEAD >future.tar
 '