That's how SwiftUI view that deal with Date value work: DatePicker and Text<Subject>(Subject, formatter: Formatter).
The problem is the new Text<F>(F.FormatInput, format: F) only use Locale from environment, but not for TimeZone and Calendar. I think it's a bug I reported FB9217356.
Look at this example, the second Text use the Locale, Timezone and Calendar from the environment, the first Text only use Locale from environment:
static let when = Date(timeIntervalSince1970: 15*3600)
static let locale = Locale(identifier: "en_US_POSIX")
static let timeZone = TimeZone(identifier: "UTC")!
static let localeChina = Locale(identifier: "zh_Hans_CN")
static let calendar = Calendar(identifier: .chinese)
static let dateFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .long
formatter.timeStyle = .long
return formatter
}()
var body: some View {
// this one only use locale from environment, not timezone and calendar. it's a bug
Text(Self.when, format: Date.FormatStyle.dateTime.locale(Self.locale))
.environment(\.locale, Self.localeChina) // it's using this locale, not the one set above
.environment(\.timeZone, Self.timeZone) // but it's not using this, still at system default
.environment(\.calendar, Self.calendar) // and not this
// this surely has to show "15:00", right?
// nope... "1/1/1970, 4:00 PM"
// same with en_US. slightly better but still wrong with en_UK (16:00)
// this one use locale, timezone and calendar from environment:
Text(Self.when, formatter: Self.dateFormatter)
.environment(\.locale, Self.localeChina) // it's using this
.environment(\.timeZone, Self.timeZone) // and this
.environment(\.calendar, Self.calendar) // and this
}