Detect iPhone 24-Hour time setting

Question

I\'m using a UIDatePicker to select a time. I am also customising the background of the picker, however I need 2 different images depending on whether the user is using 12 hour

Answer 1

Swift (3.x) version of two most popular solutions in form of Date extension :

extension Date {

    static var is24HoursFormat_1 : Bool  {
        let dateString = Date.localFormatter.string(from: Date())

        if dateString.contains(Date.localFormatter.amSymbol) || dateString.contains(Date.localFormatter.pmSymbol) {
            return false
        }

        return true
    }

    static var is24HoursFormat_2 : Bool {
        let format = DateFormatter.dateFormat(fromTemplate: "j", options: 0, locale: Locale.autoupdatingCurrent)
        return !format!.contains("a")
    }

    private static let localFormatter : DateFormatter = {
        let formatter = DateFormatter()

        formatter.locale    = Locale.autoupdatingCurrent
        formatter.timeStyle = .short
        formatter.dateStyle = .none

        return formatter
    }()
}

Usage :

Date.is24HoursFormat_1
Date.is24HoursFormat_2

Swift (2.0) version of two most popular solutions in form of NSDate extension :

extension NSDate {

    class var is24HoursFormat_1 : Bool  {
        let dateString = NSDate.localFormatter.stringFromDate(NSDate())

        if dateString.containsString(NSDate.localFormatter.AMSymbol) || dateString.containsString(NSDate.localFormatter.PMSymbol) {
            return false
        }

        return true
    }

    class var is24HoursFormat_2 : Bool {
        let format = NSDateFormatter.dateFormatFromTemplate("j", options: 0, locale: NSLocale.autoupdatingCurrentLocale())
        return !format!.containsString("a")
    }

    private static let localFormatter : NSDateFormatter = {
        let formatter = NSDateFormatter()

        formatter.locale    = NSLocale.autoupdatingCurrentLocale()
        formatter.timeStyle = .ShortStyle
        formatter.dateStyle = .NoStyle

        return formatter
    }()
}

Please note that Apple says following on NSDateFormatter (Date Formatters) :

Creating a date formatter is not a cheap operation. If you are likely to use a formatter frequently, it is typically more efficient to cache a single instance than to create and dispose of multiple instances. One approach is to use a static variable.

Thats the reason for static let

Secondly you should use NSLocale.autoupdatingCurrentLocale() ( for is24HoursFormat_1 ), that way you will always get the actual current state.