Value objects: money, units and instants

Every amount, quantity and moment in an Expo app is stored once, in one canonical integer form (minor units plus an ISO 4217 code, a canonical unit, epoch milliseconds), changed only by pure tested functions that never lose or invent a minor unit, and turned into text only at the edge, so a language, digits or unit-system change on iOS or Android never corrupts a stored value. Two zero-dependency checkers prove it on the app's own code.

Rules that must hold