Example of 2D t_reion(r) map from a ζ = 55 21cmFAST model. The darker the region, the sooner it reionised. In this scenario (and for the whole ζ55 dataset), the time of reionisation of the first HII regions is approximately 0.15 Gyr (z ≈ 20, darkest spots), and the last HI regions are reionised at around 1.1 Gyr (z ≈ 5.5, brightest regions). The mean value is 0.61 Gyr (z ≈ 8.4). This t_reion(r) map is associated with Fig. 1, taken at the same depth in the simulation box.