カレンダー周り。日本語アプリでも英語表示したい部分もあると思うので

CalendarUtil.swift

//
//  CalendarUtil.swift
//  Musubi
//
//  Created by はるふ on 2016/10/26.
//  Copyright © 2016年 はるふ. All rights reserved.
//

import Foundation

class CalendarUtil {
    static let calendar = Calendar(identifier: .gregorian)
    
    static func getComponents(_ components: Set<Calendar.Component>, from: Date) -> DateComponents {
        return calendar.dateComponents(components, from: from)
    }
    
    // 1~7 -> 日〜土
    static func getWeekdaySymbol(_ weekday: Int) -> String {
        let weekdayIndex = ((weekday-1) % 7)
        let formatter = DateFormatter()
        formatter.locale = Locale.current
        return formatter.shortWeekdaySymbols[weekdayIndex]
    }
    
    // 1〜7 -> Sunday〜Saturday
    static func getWeekdaySymbolLongEnglish(_ weekday: Int) -> String {
        let weekdayIndex = ((weekday-1) % 7)
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        return formatter.weekdaySymbols[weekdayIndex]
    }
    
    // 1〜12 -> January　〜　December
    static func getMonthSymbolLongEnglish(_ month: Int) -> String {
        let monthIndex = ((month-1) % 12)
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        return formatter.monthSymbols[monthIndex]
    }
    
    // Date -> 12:34
    static func getTime24String(from date: Date) -> String {
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.dateFormat = "HH:mm"
        return formatter.string(from: date)
    }
    
    // Date -> 2015/9, 9/2015
    static func getYearMonthString(from date: Date, locale: Locale = Locale.current) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = DateFormatter.dateFormat(fromTemplate: "yM", options: 0, locale: locale)!
        return formatter.string(from: date)
    }
    
    // Date -> 12月34日
    static func getDateString(from date: Date) -> String {
        let formatter = DateFormatter()
        formatter.dateStyle = .medium
        formatter.timeStyle = .none
        return formatter.string(from: date)
    }   
}