The maxim means that a contemporaneous exposition is the best and strongest in law.
The maxim contemporanea expositio as laid down by Lord Coke was applied to construing ancient statutes, but usually not applied to interpreting statutes which are comparatively modern. Thus, old statutes should be interpreted as they would have been at the date when they were passed.
Usages and practice developed under a statute is indicative of the meaning ascribed to its words by contemporary opinion and in case of an ancient statute, such reference to usage and practice is admissible.