وَمِنَ الْمُهِمِّ أَيْضًا مَعْرِفَةُ مَوَالِيدِهِمْ وَوَفَيَاتِهِمْ
Knowledge of transmitters’ birth and death dates is also essential.
Chronology is a basic means of testing claimed encounters. If the lifetimes do not overlap, direct hearing is impossible; if they do overlap, the fact of hearing still needs independent investigation.
Useful chronology can also include journeys, residences, age at audition, the onset of memory deterioration, and when a specific teacher was heard. An error in a single such date can change the conclusion about continuity in the chain.