Aching or tired legs are such a common symptom that many people feel it is normal at the end of a long day on their feet.  In fact, normal legs with good arterial and venous circulation shouldn't cause such symptoms and this is very often a sign of chronic venous insufficiency which usually means you have varicose veins which are not always visible on the skin surface.  If your symptoms of aching and tired legs are significant and there may be other symptoms like ankle swelling, itchy skin on the lower legs, restless legs then it is a good idea to see a phlebologist (vein doctor) and arrange for an ultrasound scan of the lower legs.