De Temporum Ratione (The Reckoning of Time)

Bede's De Temporum Ratione, The Reckoning of Time, completed in 725, is a work with no publication year in the modern sense since it survives as a manuscript composition rather than a printed edition, and its fifteenth chapter, De mensibus Anglorum, is the sole surviving ancient textual witness to the Anglo-Saxon goddess Eostre and to the goddess Hretha, both mentioned only because Bede names the months once dedicated to them. Bede was an eighth century monk and scholar working within living memory of pre-Christian Anglo-Saxon practice, though writing as a Christian describing customs he considered superseded. Its strength is that it is the only ancient source for these two names at all; without it neither would be attested anywhere. Its limit is exactly that singularity: a claim about Eostre's worship, character or wider following rests on one brief mention from an author writing a century after Christianization, not on independent corroboration.