The Historical Record
The sources for Leonidas are sparse and not fully consistent. The Synaxarion remembers him as bishop of Athens and preserves verses lamenting his departure, in which the city is left in sudden darkness: a memory of a shepherd whose loss was felt as the loss of light. Beyond his episcopal office and the April 15 commemoration, little biographical detail has come down.
The in-repo record, which is the authority followed here, places Leonidas in the third century and counts him a hieromartyr martyred about the year 250. Some reference works instead describe a Leonidas, bishop of Athens, of roughly the sixth century who reposed in peace, and the scholar Eustratiades observed that essentially nothing survives of him beyond that he was bishop of the city. These divergent datings reflect the difficulty of reconstructing an early local episcopate from later liturgical memory.