"It is wasted time."
Translation:C'est une perte de temps.
Actually "C'est du temps de perdu" is correct, the de is optional here. Adding it gives doesn't really change the meaning, but it sounds somewhat better with it, you can find it for instance in "c'est une bonne chose de faite" or "quelque chose de bien". I can't justify why it's correct to use it there, but it is nontheless.