diff --git a/inc/Gtfs/Calendar/CalendarDay.php b/inc/Gtfs/Calendar/CalendarDay.php
new file mode 100644
index 0000000..12b6667
--- /dev/null
+++ b/inc/Gtfs/Calendar/CalendarDay.php
@@ -0,0 +1,51 @@
+<?php
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: proto/gtfs.proto
+
+namespace Gtfs\Calendar;
+
+use UnexpectedValueException;
+
+/**
+ * Protobuf type <code>gtfs.Calendar.CalendarDay</code>
+ */
+class CalendarDay
+{
+    /**
+     * Generated from protobuf enum <code>NOT_AVAILABLE = 0;</code>
+     */
+    const NOT_AVAILABLE = 0;
+    /**
+     * Generated from protobuf enum <code>AVAILABLE = 1;</code>
+     */
+    const AVAILABLE = 1;
+
+    private static $valueToName = [
+        self::NOT_AVAILABLE => 'NOT_AVAILABLE',
+        self::AVAILABLE => 'AVAILABLE',
+    ];
+
+    public static function name($value)
+    {
+        if (!isset(self::$valueToName[$value])) {
+            throw new UnexpectedValueException(sprintf(
+                    'Enum %s has no name defined for value %s', __CLASS__, $value));
+        }
+        return self::$valueToName[$value];
+    }
+
+
+    public static function value($name)
+    {
+        $const = __CLASS__ . '::' . strtoupper($name);
+        if (!defined($const)) {
+            throw new UnexpectedValueException(sprintf(
+                    'Enum %s has no value defined for name %s', __CLASS__, $name));
+        }
+        return constant($const);
+    }
+}
+
+// Adding a class alias for backwards compatibility with the previous class name.
+class_alias(CalendarDay::class, \Gtfs\Calendar_CalendarDay::class);
+