我发现了下面的解决方案。根据测试，它对台湾和德国都很有效。希望它对其他地区也能很好地工作。如果没有，请让我知道错误。谢谢。

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale.current
dateFormatter.dateStyle = .none
dateFormatter.timeStyle = .short

let amSymbol: String? = dateFormatter.amSymbol
let pmSymbol: String? = dateFormatter.pmSymbol

guard let amSymbol = amSymbol, let pmSymbol = pmSymbol else {
    print("24-hour format")
}

let dateAsString = dateFormatter.string(from: Date())

if dateAsString.contains(amSymbol) || dateAsString.contains(pmSymbol) {
    print("12-hour format")
} else {
    print("24-hour format")
}