Testing must-revalidate: true required an expiration date in the future, which exposed a round-tripping problem from translating NSDate to time_point based on now(). Use epoch of 1970 instead (although technically it's not guaranteed to be the epoch for system_clock until C++20)
Darwin
The code in the Darwin platform targets Apple platforms but is not specific to iOS or macOS. This code is not distributed as an SDK in itself, but is required by the Mapbox iOS SDK and Mapbox macOS SDK.
These files depend on the Foundation and Core Foundation frameworks but do not depend on iOS- or macOS–specific frameworks, such as UIKit or AppKit. Any non-cross-platform code is guarded by TargetConditionals.h macros.