ἐν δὲ μηνὸς πρῶτον τύχεν ἆμαρ → it chanced to be on the first of the month, that day fell on the first of the month
SourceGerman (Pape)
[Seite 245] ἡ, dasselbe, Xen. Cyn. 5, 18; Plut. oft, z. B. ὥσπερ ἐν τοῖς ἐσόπτροις τὰ φαινόμενα κατ' ἀνταύγειαν de gen. Socr. 22 (p. 347).