The elimination of anti-hadrons was completed by one second after the Big Bang, when the following lepton epoch began.

After most leptons and anti-leptons are annihilated at the end of the lepton epoch the energy of the universe is dominated by photons.

During the lepton epoch the temperature of the universe was still high enough to create lepton/anti-lepton pairs, so leptons and anti-leptons were in thermal equilibrium.

In physical cosmology, the lepton epoch was the period in the evolution of the early universe in which the leptons dominated the mass of the universe.

The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang.