fix: reject an out-of-range date-time offset

Assisted-by: GLM 5.3 Flash

interpres_test.go

@@ -380,6 +380,34 @@ func TestRejectsInvalidNumbers(t *testing.T) {
 	}
 }
 
+func TestParseRejectsOffsetOutOfRange(t *testing.T) {
+	for _, tok := range []string{
+		"1979-05-27T07:32:00+00:60",
+		"1979-05-27T07:32:00-00:99",
+		"1979-05-27T07:32:00+24:00",
+		"1979-05-27T07:32:00+99:99",
+	} {
+		if _, err := Parse([]byte("v = " + tok + "\n")); err == nil {
+			t.Errorf("%q: expected an error, got none", tok)
+		}
+	}
+}
+
+func TestParseAcceptsOffsetBounds(t *testing.T) {
+	tree, err := Parse([]byte("a = 1979-05-27T07:32:00+23:59\nb = 1979-05-27T07:32:00-23:59\n"))
+	if err != nil {
+		t.Fatalf("parse: %v", err)
+	}
+	a := tree["a"].(time.Time)
+	if _, offset := a.Zone(); offset != 23*3600+59*60 {
+		t.Fatalf("a offset = %d, want %d", offset, 23*3600+59*60)
+	}
+	b := tree["b"].(time.Time)
+	if _, offset := b.Zone(); offset != -(23*3600 + 59*60) {
+		t.Fatalf("b offset = %d", offset)
+	}
+}
+
 func TestAcceptsNumberEdgeCases(t *testing.T) {
 	cases := map[string]any{
 		"0":           int64(0),