A day's journey in pre-modern literature, including the Bible,^[1][2] ancient geographers and ethnographers such as Herodotus, is a measurement of distance.

In the Bible, it is not as precisely defined as other Biblical measurements of distance; the distance has been estimated from 32 to 40 kilometers (20 to 25 miles). Judges 19 records a party of three people and two mules who traveled from Bethlehem to Gibeah, a distance of about 10 miles, in an afternoon. Porter^[3] notes that a mule can travel about 3 miles per hour, covering 24 miles in an eight-hour day.

In a translation by J. B. Bury (Priscus, fr. 8 in Fragmenta Historicorum Graecorum) We set out with the barbarians, and arrived at Sardica, which is thirteen days for a fast traveller from Constantinople. From Constantinople-Istanbul to Sofia is 550–720 km distance at a pace between 42 and 55 km /day.

Based on a comprehensive review of references in Herodotus, Geus^[4] concludes that "Herodotus has a very well-defined notion of what distance a traveller can cover under normal circumstances in a day (between 150 and 200 stades or roughly, between 27 and 40 kilometres)," though he cites some exceptional examples of over 100 km per day.