The estimation of the post-mortem interval is one of the fundamental aspects in Forensic Anthropology. The legal significance is that the establishment of time since the death of the individual can determine the prescription or not a crime; however it is an issue difficult to resolve. In bone analysis, although there are signs indicative or suggestive of a certain time since death, there is no truly reliable or ideal method. The taphonomic factor greatly influences the development of procedures for estimating post-mortem interval and within taphonomy, variability is the rule. Currently, forensic anthropologists use a combination of some of the known methods; they can only be approximated with a high margin of error. We review some of these methods and especially the calcination method, for which a modification is proposed, eliminating moisture bone prior to the analysis.