ὅτου

From LSJ

Βίων δύο ἔλεγε διδασκαλίας εἶναι θανάτου, τόν τε πρὸ τοῦ γενέσθαι χρόνον καὶ τὸν ὕπνονBion used to say that we have two teachers for death: the time before we were born and sleep | Bion said that there are two rehearsals for death: the time before being born and sleep

Source

French (Bailly abrégé)

att. p. οὗτινος, gén. de ὅστις.

English (Abbott-Smith)

ὅτου v.s. ὅστις

English (Strong)

for the genitive case of ὅστις (as adverb); during which same time, i.e. whilst: whiles.

Russian (Dvoretsky)

ὅτου: (= οὗτινος) gen. к ὅστις.