Laudator Temporis Acti

There is a Greek expression λευκὴ ἡμέρα (leukē hēmera = white day), which the Suda (Λ 323 Adler, tr. Timothy Pepper) explains as follows:

The good [kind]. From the proverb speaking "of the things for a quiver". For Phylarchus says that the Scythians, when they were about to lie down to sleep, brought the quiver, and if they happened to have passed that day unharmed, they placed a white pebble on the quiver, but if [things had gone] troublesomely, [they placed] a black one. Accordingly, in the case of men who were dying, they brought out their quivers and counted the pebbles; and if many white ones were found, they declared the departed fortunate. Whence the proverb.

Λευκὴ ἡμέρα: ἡ ἀγαθή. ἀπὸ τῆς παροιμίας τῆς λεγούσης τῶν εἰς φαρέτραν. Φύλαρχος γάρ φησι τοὺς Σκύθας μέλλοντας καθεύδειν ἄγειν τὴν φαρέτραν, καὶ εἰ μὲν ἀλύπως τύχοιεν τὴν ἡμέραν ἐκείνην διαγαγόντες, καθιέναι εἰς τὴν φαρέτραν ψῆφον λευκήν, εἰ δὲ ὀχληρῶς, μέλαιναν. ἐπὶ τοίνυν τῶν ἀποθνησκόντων ἐκφέρειν τὰς φαρέτρας καὶ ἀριθμεῖν τὰς ψήφους: καὶ εἰ εὑρεθείησαν πολλαὶ λευκαί, εὐδαιμονίζειν τὸν ἀπογενόμενον. ὅθεν ἡ παροιμία.

Pliny the Elder, Natural History 7.131 (tr. John Bostock and H.T. Riley), is similar, substituting Thracians for Scythians and urns for quivers:

Mortals, vain as they are, and ingenious in deceiving themselves, calculate in the same way as the Thracians, who, according to their experience of each day, deposit in an urn a black or a white pebble: at the close of their life, these pebbles are separated, and from the relative number of each kind, they form their conclusions.

vana mortalitas et ad circumscribendam se ipsam ingeniosa conputat more Thraciae gentis, quae calculos colore distinctos pro experimento cuiusque diei in urnam condit ac supremo die separatos dinumerat atque ita de quoque pronuntiat.