timezone_playground.swift

gistfile1.txt

import SwiftUI

fileprivate extension Date.FormatStyle {
    func withTimeZone(_ timeZone: TimeZone?) -> Date.FormatStyle {
        var copy = self
        if let timeZone = timeZone {
            copy.timeZone = timeZone
        }
        return copy
    }
}

struct TimeZonePlayground: View {
    @State private var date = Date()
    
    var body: some View {
        VStack {
            DatePicker("Korea", selection: $date, displayedComponents: [.date, .hourAndMinute])
                .environment(\.timeZone, TimeZone(identifier: "Asia/Seoul")!)
            
            DatePicker("US", selection: $date, displayedComponents: [.date, .hourAndMinute])
                .environment(\.timeZone, TimeZone(identifier: "America/New_York")!)
            
            DatePicker("Paris", selection: $date, displayedComponents: [.date, .hourAndMinute])
                .environment(\.timeZone, TimeZone(abbreviation: "CET")!)
            
            // User/Device Date Picker
            DatePicker("Local", selection: $date, displayedComponents: [.date, .hourAndMinute])
            
            //Timezone conversion by Date.FormatStyle
            GroupBox("Date.FormatStyle") {
                Text(date.formatted(Date.FormatStyle(timeZone: TimeZone(identifier: "Asia/Seoul")!).hour().minute().day().month().year().timeZone(.specificName(.long))))
                Text(date.formatted(Date.FormatStyle(timeZone: TimeZone(identifier: "America/New_York")!).hour().minute().day().month().year().timeZone(.specificName(.long))))
                Text(date.formatted(Date.FormatStyle(timeZone: TimeZone(identifier: "CET")!).hour().minute().day().month().year().timeZone(.specificName(.long))))
                Text(date.formatted(Date.FormatStyle().hour().minute().day().month().year().timeZone(.specificName(.long))))
            }
            .font(.caption)
            
            
            //Timezone conversion with extension .withTimeZone
            let dfTzLong = Date.FormatStyle().day().month().year().hour().minute().timeZone(.specificName(.long))
            let dfTzShort = Date.FormatStyle().day().month().year().hour().minute().timeZone(.specificName(.short))
            
            GroupBox(".withTimeZone extension") {
                
                Text(date.formatted(dfTzLong.withTimeZone(TimeZone(identifier: "Asia/Seoul"))))
                Text(date.formatted(dfTzLong.withTimeZone(TimeZone(identifier: "America/New_York"))))
                Text(date.formatted(dfTzLong.withTimeZone(TimeZone(identifier: "CET"))))
                Text(date.formatted(dfTzLong.withTimeZone(nil)))
                
                let _ = print(date.formatted(dfTzShort.withTimeZone(TimeZone(identifier: "America/New_York"))))
                //                Text(date.formatted(.dateTime.day().month().year().hour().minute().timeZone(.specificName(.long)).withTimeZone(TimeZone(identifier: "Asia/Seoul"))))
                //                Text(date.formatted(.dateTime.day().month().year().hour().minute().timeZone(.specificName(.long)).withTimeZone(TimeZone(identifier: "America/New_York"))))
                //                Text(date.formatted(.dateTime.day().month().year().hour().minute().timeZone(.specificName(.long)).withTimeZone(TimeZone(identifier: "CET"))))
                //                Text(date.formatted(.dateTime.day().month().year().hour().minute().timeZone(.specificName(.long)).withTimeZone(nil)))
                
            }
            .font(.caption)
            
            
            //Timezone conversion by function and DateFormatter
            GroupBox("DateFormatter") {
                Text(dateFormatterTz(date, timeZone: TimeZone(identifier: "Asia/Seoul")))
                Text(dateFormatterTz(date, timeZone: TimeZone(identifier: "America/New_York")))
                Text(dateFormatterTz(date, timeZone: TimeZone(identifier: "CET")))
                Text(dateFormatterTz(date, timeZone: Locale.current.timeZone))
            }
            .font(.caption)
            
        }
        .padding()
        
        
    }
    
    
    
    private func dateFormatterTz(_ initDate: Date = Date(), timeZone: TimeZone? = nil) -> String {
        let formatter = DateFormatter()
        formatter.dateStyle = .short
        formatter.timeStyle = .full
        
        if let timeZone = timeZone {
            formatter.timeZone = timeZone
        }
        return formatter.string(from: initDate)
    }
    
}

#Preview {
    TimeZonePlayground()
}