Epoch of reionization (EoR) neutral hydrogen (H i) 21-cm signal evolves significantly along the line-of-sight (LoS) due to the light-cone (LC) effect. It is important to accurately incorporate this in simulations to correctly interpret the signal. 21-cm LC simulations are typically produced by stitching together slices from a finite number \((N_{\textrm{RS}})\) of ‘reionization snapshot’, each corresponding to a different stage of reionization. In this paper, we have quantified the errors in 21-cm LC simulation due to the finite value of \(N_{\textrm{RS}}\) . We show that this can introduce large discontinuities (>200%) at the stitching boundaries when \(N_{\textrm{RS}}\) is small \((=2,4)\) and the mean neutral fraction jumps by \(\delta \bar{x}_{\textrm{H}\,\textsc {i}} =0.2,0.1\) , respectively, at the stitching boundaries. This drops to 17% for \(N_{\textrm{RS}}=13\) , where \(\delta \bar{x}_{\textrm{H}\,\textsc {i}}=0.02\) . We found that we can achieve \(\delta \bar{x}_{\textrm{H}\,\textsc {i}} \le 0.01\) with \(N_{\textrm{RS}}=26\) , and we use this as reference for comparing the other simulations. We presented and also validated a method for mitigating this error by increasing \(N_{\textrm{RS}}\) without a proportional increase in the computational costs, which are mainly incurred in generating the dark matter and halo density fields. Our method generates these fields, only at a few redshifts, and interpolates them to generate reionization snapshots at closely spaced redshifts. We used this to generate 21-cm LC simulations with \(N_{\textrm{RS}}=51\) , 101, 201, and showed that the errors reduce as \(N_{\textrm{RS}}^{-1}\) .
