Swift DateFormat like apple mail

date+localizedString.swift

import Cocoa

extension Calendar {
    func isDateIn7days(from date: Date) -> Bool {
        let date1 = self.startOfDay(for: Date())
        let date2 = self.startOfDay(for: date)
        
        let days = (date1 - date2).day ?? 0
        return days <= 8 && days > 0
    }
}

extension Date {

    static func - (lhs: Date, rhs: Date) -> DateComponents {
        let calendar = Calendar.current
        return calendar.dateComponents([.day], from: rhs, to: lhs)
    }
    
    var formattedRelativeString: String {
        let calendar = Calendar.current
        let dateFormatter = DateFormatter()
        
        switch self {
        case let date where calendar.isDateInToday(date):
            dateFormatter.timeStyle = .short
        case let date where calendar.isDateInYesterday(date):
            dateFormatter.dateStyle = .short
            dateFormatter.doesRelativeDateFormatting = true
        case let date where calendar.isDateIn7days(from: date):
            dateFormatter.dateFormat = "EEEE"
        default:
            dateFormatter.dateStyle = .short
        }
        
        return dateFormatter.string(from: self)
    }
    
}


let calendar = Calendar.current
let today = Date()
Array(0...10).reversed().forEach { value in
    let date = calendar.date(byAdding: .day, value: -value, to: today)!
    print( date.formattedRelativeString)
}