Second only to photons, neutrinos are by far the most abundant particles in the universe, and their presence and properties affect the evolution of the universe in several different ways. Back on Earth neutrino properties are studied in various neutrino oscillation experiments, which have shown us, for example, that neutrinos have non-zero masses. Several anomalies in these experiments have hinted towards the existence of one or more sterile neutrino species. These are additional non-standard neutrinos that don't feel the weak nuclear force. Recently a global analysis of detections of neutrinos from nuclear reactors showed that the data prefer a scenario with two such sterile neutrino species. We have investigated the consequences that the existence of these additional neutrinos will have for cosmology. We find that the universe is a billion years younger than previously thought, and dark energy should be described by something different than a cosmological constant. That is, if the nuclear reactor neutrino experiments are not fooling us.