Big Bang
The Big Bang is generally linked to the singularity space-time called birth of the Universe. The space and the time are intimately linkde and the time has been then created during the creation of the space.
Actually, the Big Bang matches to the emission of energy created during the generation of the matter and the antimatter. The radiation caused per this emission exists in all the Universe and is called the 3K (3 Kelvin degrees). This is via this radiation, via the hubble constant and via observations of celestial objects extremely far away such as the quasars that we have been able to give an estimate of the age of the Universe equal to 13,7 billion years, plus or minus 1%.
See matter, antimatter, relativity, Hubble constant, quasar, constant of Planck, distance of Planck, time od Planck.