Ordination of Caluppa took place between 571, the year of Avitus' ascension to the bishopric, and 573, year of Gregory of Tours' promotion to bishopric of Tours. Year of Caluppa's death, i.e. 576, is known from Gregory of Tours' Histories 5.9.
The ordination of hermits to the presbyterate is attested by Gregory of Tours several times; see e.g. Winnocus  and Patroclus . There could be a number of reasons for such an ordination, such as: 1) the opportunity for a bishop to have a holy person within his clergy; 2) to assume ecclesiastical control over him; 3) to make sure he does not leave the neighbourhood.