- The temporal unit. Al-Dhahabī did not abide by a fixed span of years in those works he organized by strata. Consequently, he did not record the deaths of his subjects with strict chronological boundaries: the dates of death overlap from one stratum to the next, and, at the same time, the length of each stratum varies greatly.
In Tadhkirat al-Ḥuffāẓ, for example, the deaths of the figures placed in the first stratum run from 13 AH—the year Abū Bakr al-Ṣiddīq passed away—to 93 AH, the year Anas ibn Mālik died. Thus the first stratum covers eighty years.
As for the Followers (tābiʿūn), al-Dhahabī divides them in the Tadhkira into three strata:
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Senior Followers: their deaths extend from 62 AH, the year ʿAlqama ibn Qays al-Nakhaʿī died, to 107 AH, the year—according to al-Dhahabī’s preferred view—in which Rajāʾ al-ʿAṭāridī passed away, a span of forty-five years.
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The middle tier of Followers: the deaths recorded here range from 93 AH to 117 AH, a span of twenty-four years.
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A third tier of Followers: their deaths fall between 113 AH and 151 AH, making thirty-eight years.
The fifth stratum runs from 144 AH to 180 AH—thirty-six years—and so forth.
The disparity I have noted in the duration of the early strata in the Tadhkira is likewise found in the later ones. The twentieth stratum extends from 667 AH to 708 AH, i.e. forty-one years, whereas the twenty-first—and last—stretches from 672 AH to 742 AH, the year the ḥadīth master al-Mizzī died, amounting to seventy years.
This pronounced inconsistency in the length of the strata in the Tadhkira is also evident in Siyar Aʿlām al-Nubalāʾ: the duration of Stratum Thirty amounted to