diff --git a/ledger/group.go b/ledger/group.go
new file mode 100644
index 0000000..82ea816
--- /dev/null
+++ b/ledger/group.go
@@ -0,0 +1,21 @@
+package ledger
+
+import "regexp"
+
+type Group func(Delta) Delta
+
+func GroupDate(pattern string) Group {
+	p := regexp.MustCompile(pattern)
+	return func(d Delta) Delta {
+		d.Date = p.FindString(d.Date)
+		return d
+	}
+}
+
+func GroupName(pattern string) Group {
+	p := regexp.MustCompile(pattern)
+	return func(d Delta) Delta {
+		d.Name = p.FindString(d.Name)
+		return d
+	}
+}
diff --git a/ledger/group_test.go b/ledger/group_test.go
new file mode 100644
index 0000000..8a321bb
--- /dev/null
+++ b/ledger/group_test.go
@@ -0,0 +1,13 @@
+package ledger
+
+import "testing"
+
+func TestGroup(t *testing.T) {
+	if got := GroupDate("^20..")(Delta{Date: "2021-01"}); got.Date != "2021" {
+		t.Error(got)
+	}
+
+	if got := GroupName("^[^:]*")(Delta{Name: "a:b:c"}); got.Name != "a" {
+		t.Error(got)
+	}
+}