A Day's journey
in pre-modern literature, including the Bible
, ancient geographers and ethnographers such as Herodotus
, is a measurement of distance.
Not precisely defined in the Bible, the distance has been estimated from 32 to 40 kilometers (20-25 miles). The term "a day's journey" is used in Numbers 11:31 and Kings 19:4.
In 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-Istambul to Sofia is 550-720 km distance it give 42 - 55 km /day.