Localized Date Formatting

1-Example.swift

// US locale:
// Oct 14, 2020, 7:50 PM
Date().format(with: [.monthShort, .dayOfMonth, .yearFull, .hour, .minute], locale: Locale(identifier: "en_US"))!

// French locale:
// 14 Oct 2020 à 19:50
Date().format(with: [.monthShort, .dayOfMonth, .yearFull, .hour, .minute], locale: Locale(identifier: "fr"))!

2-LocalizedDateFormatting.swift

import Foundation

extension Date {
  
  // MARK: - Helper types
  
  enum DateFormatComponents: String {
    /// 1997
    case yearFull = "yyyy"
    /// 97 (1997)
    case yearShort = "yy"
    
    /// 7
    case monthDigit = "M"
    /// 07
    case monthDigitPadded = "MM"
    /// Jul
    case monthShort = "MMM"
    /// July
    case monthFull = "MMMM"
    /// J (July)
    case monthLetter = "MMMMM"
    
    /// 5
    case dayOfMonth = "d"
    
    /// Sat
    case weekdayShort = "EEE"
    /// Saturday
    case weekdayFull = "EEEE"
    /// S (Saturday)
    case weekdayLetter = "EEEEE"
    
    /// Localized **13** or **1 PM**, depending on the locale.
    case hour = "j"
    /// 20
    case minute = "m"
    /// 08
    case second = "ss"
    
    /// CST
    case timeZone = "zzz"
    /// **Central Standard Time** or **CST-06:00** or if full name is unavailable.
    case timeZoneFull = "zzzz"
  }
  
  
  // MARK: - Date Math
  
  func advance(_ component: Calendar.Component, by value: Int, calendar: Calendar = Calendar.current) -> Date? {
    return calendar.date(byAdding: component, value: value, to: self)
  }
  
  func isSame(_ granularity: Calendar.Component, as other: Date, calendar: Calendar = Calendar.current) -> Bool {
    return calendar.compare(self, to: other, toGranularity: granularity) == .orderedSame
  }
  
  
  // MARK: - Date Formatting
  
  func format(
    with components: [DateFormatComponents],
    in timeZone: TimeZone? = .current,
    using dateFormatter: DateFormatter = DateFormatter(),
    locale: Locale = .current) -> String? {
    let template = components.map(\.rawValue).joined(separator: " ")
    
    guard let localizedFormat = DateFormatter.dateFormat(fromTemplate: template, options: 0, locale: locale) else {
      return nil
    }
    
    dateFormatter.timeZone = timeZone
    dateFormatter.dateFormat = localizedFormat
    
    return dateFormatter.string(from: self)
  }
}