chore: add missing license header

GitOrigin-RevId: e877e7dec67cb3ac39186eabb1a6765666656d67
diff --git a/src/inc/date.php b/src/inc/date.php
index ba89c09..742a4be 100644
--- a/src/inc/date.php
+++ b/src/inc/date.php
@@ -1,4 +1,23 @@
 <?php
+/*
+ * hores
+ * Copyright (c) 2023 Adrià Vilanova Martínez
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this program.
+ * If not, see http://www.gnu.org/licenses/.
+ */
+
 class date {
   const LOCALE = 'es';