I cannot find anyway to format hour in 24 hour with the new Date.FormatStyle
import Foundation
let afternoonHour = try Date("2021-10-23T02:37:12Z", strategy: .iso8601)
// this format to 24 hour
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm:ss"
let twentyFourHour = dateFormatter.string(from: afternoonHour)
print(twentyFourHour)
// with the new Date.FormatStyle
// how to display hour in 24hr format?
afternoonHour.formatted(.dateTime.month().day().hour(.conversationalTwoDigits(amPM: .wide)).minute().timeZone(.specificName(.short))) // "Oct 22, 07:37 PM PDT"
afternoonHour.formatted(.dateTime.hour(.conversationalDefaultDigits(amPM: .omitted))) // "07"
// how to get "19"?
Let’s start by digging into your DateFormatter example. Consider this code:
// this format to 24 hour
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm:ss"
let twentyFourHour = dateFormatter.string(from: afternoonHour)
print(twentyFourHour)
This doesn’t work the way you think it does. Try this:
Set your Mac to a 24-hour by default locale (like the UK).
Put that code into a Xcode playground. It’ll print a 24-hour time:
20:52:54
Go to System Preferences > Language & Region > General and uncheck 24-Hour Time.
Run your playground again; this time you get a 12 hour time:
8:52:54 pm
That’s because you haven’t pinned the locale on the date formatter to en_US_POSIX. Without that, the date formatter uses the user’s settings, and that includes this 12-/24-hour override.
The issue here is that DateFormatter serves two roles:
By default it works with user-visible dates.
If you pin the locale to en_US_POSIX you can use it to work with fixed-format dates.
Right now you’re crossing those streams, which doesn’t end well.
AFAIK Foundation’s new date formatting support is intended to support the first role, not the second. If you want to work with fixed-format dates, you have various options:
ISO8601DateFormatter
DateFormatter with the locale pinned to en_US_POSIX
Ah, I forgot. This is not a bug, it's how Text works: it ignores the locale set in the FormatStyle and use the environment. However, it doesn't seem to do the same for Calendar and TimeZone. It should, though, like the DatePicker:
import SwiftUI
struct ContentView: View {
static let calendar = Calendar(identifier: .chinese)
static let locale = Locale(identifier: "zh_Hans_CN")
static let timeZone = TimeZone(identifier: "Asia/Shanghai")!
static let dateFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateFormat = "HH:mm:ss.SSSz"
return formatter
}()
@State private var when = Date(timeIntervalSinceReferenceDate: 656904575.211251)
var body: some View {
VStack {
// default
Text(when, format: .dateTime.month().day().hour().minute().timeZone(.specificName(.long)))
.padding()
// New Date.FormatStyle: only locale in environment work
Text(when, format: .dateTime.month().day().hour().minute().timeZone(.specificName(.long)))
.padding()
.environment(\.locale, Self.locale) // works
// New Date.FormatStyle: timezone and calendar in environment don't work
Text(when, format: .dateTime.month().day().hour().minute().timeZone(.specificName(.long)))
.padding()
.environment(\.locale, Self.locale) // works
.environment(\.timeZone, Self.timeZone) // not work, still at system
.environment(\.calendar, Self.calendar) // not work, still at system
// old DateFormatter: only timeZone in environment work
Text(when, formatter: Self.dateFormatter)
.environment(\.locale, Self.locale) // not work
.environment(\.timeZone, Self.timeZone) // works
.environment(\.calendar, Self.calendar) // not work
// DatePicker respect all the env values
DatePicker("When", selection: $when)
// all work:
.environment(\.locale, Self.locale)
.environment(\.timeZone, Self.timeZone)
.environment(\.calendar, Self.calendar)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
that's quite non obvious... have a formatter/format parameter which is ... ignored?
struct ContentView: View {
static let when = Date(timeIntervalSince1970: 15*3600)
static let locale = Locale(identifier: "en_US_POSIX")
static let timeZone = TimeZone(identifier: "UTC")!
var body: some View {
Text(Self.when, format: Date.FormatStyle.dateTime.locale(Self.locale))
.environment(\.locale, Self.locale)
.environment(\.timeZone, Self.timeZone)
}
// 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)
}
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
}
That not what I see: my example above set a china locale in environment and it's showing in Chinese. But timezone and calendar are not used from environment.
This new Textshould work like the DateFormatter version: use locale, timezone and calendar from environment. I reported this many months ago but no fix so far. This prevents me from using the new Date.FormatStyle with Text to display Date value in specific timezone and calendar, different from user's system preference.
What I wish is Apple make it 1) follow user's 24-hour or AM/PM preference, 2) allow setting of locale, timezone and calendar work as you say, or be consisted with the current state: take them all from the environment.
until it is fixed, in my experience DateFormatter's "setLocalizedDateFormatFromTemplate" works ok. although i do not know how to ask it for "user preferred 24 or 12 hour symbol", in other words while i can pass it "h" / "hh" / "H" or "HH" i don't know which one to use to match the OS setting.
After watch What's new in Foundation again, he uses @Environment(\.locale) and pass the value into the Date.FormatStyle with .locale(locale). But .environment(\.locale, ...) seems to have precedent over what you specify:
Text(when, format: Date.FormatStyle(locale: locale1, calendar: calendar1, timeZone: timeZone1)) // <= this locale1 is not used, calendar1 and timeZone1 are used
.environment(\.locale, locale2) // <== this locale2 is used
.environment(\.calendar, calendar2) // <== this calendar2 is not used
.environment(\.timeZone, timeZone2) // <== this timeZone2 is not used
But the Date.FormatStyle.inint(...) lets you specify calendar/timezone
I'm trying to get this to work in raw Swift in a watchOS complication without SwiftUI and has been giving me issues too:
let text = Date.now.formatted(dateStyle.locale(.init(identifier: "en_US_POSIX")).hour(.twoDigits(amPM: .omitted)).minute())
CLKSimpleTextProvider(text: text)
It's displaying 11:38.. this seems like a bug because en_UK does display 23:38. That isn't ideal because what if the local isn't English to begin with, it would force English numbers.
Really what I'm looking for is a new static Date.FormatStyle.Symbol.Hour so I can do something like this: