Lewis Short
interstĭtĭum (noun N) : id.
* A space between, interstice, interval (post-Aug.).
* Of place, Macr. Somn. Scip. 1, 6; Mart. Cap. 8, § 837; Amm. 20, 3, 10.
* Of time, an interval: quantum interstitii dies habet,Mart. Cap. 6, § 601.— Plur., Mart. Cap. 6, § 600.
Charlton T. Lewis, Charles Short, A Latin Dictionary