令和対応！Swiftで和暦と西暦を変換する方法15選

import Foundation

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "ja_JP")
formatter.dateStyle = .long
formatter.calendar = Calendar(identifier: .japanese)

let now = Date()
let japaneseDateString = formatter.string(from: now)

print(japaneseDateString) // 例: 令和4年10月19日

import Foundation

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "ja_JP")
formatter.dateStyle = .long
formatter.calendar = Calendar(identifier: .japanese)

let now = Date()
let components = formatter.calendar.dateComponents([.year], from: now)
if let year = components.year {
    let reiwaYear = year - 2018 // 令和元年は2019年なので
    print("令和\(reiwaYear)年")
}

import Foundation

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "ja_JP")
formatter.dateFormat = "GGyy年MM月dd日"
formatter.calendar = Calendar(identifier: .japanese)

let now = Date()
let detailedDateString = formatter.string(from: now)

print(detailedDateString) // 例: 令和4年10月20日

import Foundation

// ユーザーからの入力を受け取る
print("西暦を入力してください：")
if let input = readLine(), let inputYear = Int(input) {

    // 令和の年を計算
    let reiwaYear = inputYear - 2018 // 令和元年は2019年なので
    if reiwaYear > 0 {
        print("入力された西暦は令和\(reiwaYear)年に該当します。")
    } else {
        print("入力された西暦は令和以前の年号に該当します。")
    }

} else {
    print("正しい西暦を入力してください。")
}

import Foundation

// 西暦を和暦に変換する関数
func convertToJapaneseEra(year: Int) -> String {
    if year >= 1989 && year <= 2018 {
        return "平成\((year - 1988)年)"
    } else if year >= 1926 && year < 1989 {
        return "昭和\((year - 1925)年)"
    } else {
        return "該当する和暦はありません"
    }
}

// ユーザーからの入力を受け取る
print("西暦を入力してください：")
if let input = readLine(), let inputYear = Int(input) {
    let result = convertToJapaneseEra(year: inputYear)
    print("入力された西暦は\(result)に該当します。")
} else {
    print("正しい西暦を入力してください。")
}

import Foundation

// 西暦を指定した和暦の範囲で変換する関数
func convertWithinEraRange(year: Int, eraName: String, eraStartYear: Int, eraEndYear: Int) -> String? {
    if year >= eraStartYear && year <= eraEndYear {
        return "\(eraName)\(year - eraStartYear + 1)年"
    }
    return nil
}

// ユーザーからの入力を受け取る
print("西暦を入力してください：")
if let input = readLine(), let inputYear = Int(input) {
    if let result = convertWithinEraRange(year: inputYear, eraName: "昭和", eraStartYear: 1926, eraEndYear: 1988) {
        print("入力された西暦は\(result)に該当します。")
    } else {
        print("入力された西暦は指定された範囲内に該当しません。")
    }
} else {
    print("正しい西暦を入力してください。")
}

import Foundation

let formatter = DateFormatter()
formatter.calendar = Calendar(identifier: .japanese)
formatter.dateStyle = .full
formatter.timeStyle = .none

let now = Date()
let dateString = formatter.string(from: now)

print("現在の日付(和暦)：\(dateString)")

import Foundation

func getJapaneseEra(year: Int) -> String {
    switch year {
    case 1868...1911:
        return "明治"
    case 1912...1925:
        return "大正"
    case 1926...1988:
        return "昭和"
    case 1989...2018:
        return "平成"
    case 2019...:
        return "令和"
    default:
        return "未知の年号"
    }
}

let inputYear = 2020
print("\(inputYear)年は\(getJapaneseEra(year: inputYear))に該当します。")

let formatter = DateFormatter()
formatter.calendar = Calendar(identifier: .japanese)
formatter.dateFormat = "GGyy年M月d日"

let date = Date()
print("今日の日付(和暦): \(formatter.string(from: date))")

import Foundation

func convertToJapaneseEra(dateString: String) -> String? {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"

    guard let date = formatter.date(from: dateString) else {
        return nil
    }

    formatter.calendar = Calendar(identifier: .japanese)
    formatter.dateFormat = "GGyy年M月d日"

    return formatter.string(from: date)
}

if let result = convertToJapaneseEra(dateString: "2023-02-30") {
    print("変換結果: \(result)")
} else {
    print("変換に失敗しました。正しい日付を入力してください。")
}

import Foundation

let formatter = DateFormatter()
formatter.calendar = Calendar(identifier: .japanese)
formatter.dateFormat = "GGyy年 (yyyy年) M月d日"

let date = Date()
print("今日の日付(カスタマイズ): \(formatter.string(from: date))")

import Foundation

func convertDatesToJapaneseEra(dates: [String]) -> [String] {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    formatter.calendar = Calendar(identifier: .japanese)
    formatter.dateFormat = "GGyy年M月d日"

    return dates.compactMap { date in
        guard let parsedDate = DateFormatter().date(from: date) else { return nil }
        return formatter.string(from: parsedDate)
    }
}

let dateStrings = ["2021-05-01", "2022-01-01", "2023-05-20"]
let convertedDates = convertDatesToJapaneseEra(dates: dateStrings)
print(convertedDates)

import Foundation

func convertJapaneseEraListToGregorian(dates: [String]) -> [String] {
    let inputFormatter = DateFormatter()
    inputFormatter.dateFormat = "GGyy年M月d日"
    inputFormatter.calendar = Calendar(identifier: .japanese)

    let outputFormatter = DateFormatter()
    outputFormatter.dateFormat = "yyyy年M月d日"

    return dates.compactMap { date in
        guard let parsedDate = inputFormatter.date(from: date) else { return nil }
        return outputFormatter.string(from: parsedDate)
    }
}

let japaneseEraDates = ["令和3年5月1日", "平成31年4月30日", "昭和64年1月7日"]
let gregorianDates = convertJapaneseEraListToGregorian(dates: japaneseEraDates)
print(gregorianDates)

import Foundation

func convertGregorianListToJapaneseEra(dates: [String]) -> [String] {
    let inputFormatter = DateFormatter()
    inputFormatter.dateFormat = "yyyy年M月d日"

    let outputFormatter = DateFormatter()
    outputFormatter.dateFormat = "GGyy年M月d日"
    outputFormatter.calendar = Calendar(identifier: .japanese)

    return dates.compactMap { date in
        guard let parsedDate = inputFormatter.date(from: date) else { return nil }
        return outputFormatter.string(from: parsedDate)
    }
}

let gregorianDatesForConversion = ["2021年5月1日", "2019年4月30日", "1989年1月7日"]
let japaneseEraDatesConverted = convertGregorianListToJapaneseEra(dates: gregorianDatesForConversion)
print(japaneseEraDatesConverted)

func japaneseEraMonthName(month: Int) -> String? {
    let monthNames = ["睦月", "如月", "弥生", "卯月", "皐月", "水無月", "文月", "葉月", "長月", "神無月", "霜月", "師走"]
    return month >= 1 && month <= 12 ? monthNames[month - 1] : nil
}

let monthNumber = 5
if let monthName = japaneseEraMonthName(month: monthNumber) {
    print("西暦の\(monthNumber)月は、和暦では「\(monthName)」と呼ばれます。")
}

import Foundation

func convertDateRangeToJapaneseEra(startDate: Date, endDate: Date) -> [String] {
    var dates: [String] = []
    let formatter = DateFormatter()
    formatter.dateFormat = "GGyy年M月d日"
    formatter.calendar = Calendar(identifier: .japanese)

    var currentDate = startDate
    let calendar = Calendar.current
    while currentDate <= endDate {
        dates.append(formatter.string(from: currentDate))
        currentDate = calendar.date(byAdding: .day, value: 1, to: currentDate)!
    }
    return dates
}

let start = DateFormatter().date(from: "2021年1月1日")!
let end = DateFormatter().date(from: "2021年1月5日")!
let japaneseEraDatesInRange = convertDateRangeToJapaneseEra(startDate: start, endDate: end)
print(japaneseEraDatesInRange)

import Foundation

enum DateConversionType {
    case gregorianToJapaneseEra
    case japaneseEraToGregorian
    // 必要に応じて他の変換形式も追加可能
}

func convertDate(_ date: String, conversionType: DateConversionType) -> String? {
    let formatter = DateFormatter()
    switch conversionType {
    case .gregorianToJapaneseEra:
        formatter.dateFormat = "yyyy年M月d日"
        formatter.calendar = Calendar(identifier: .japanese)
        if let parsedDate = DateFormatter().date(from: date) {
            return formatter.string(from: parsedDate)
        }
    case .japaneseEraToGregorian:
        formatter.dateFormat = "GGyy年M月d日"
        formatter.calendar = Calendar(identifier: .japanese)
        if let parsedDate = DateFormatter().date(from: date) {
            return formatter.string(from: parsedDate)
        }
    }
    return nil
}

let sampleDate = "2021年5月1日"
if let convertedDate = convertDate(sampleDate, conversionType: .gregorianToJapaneseEra) {
    print("変換後の日付: \(convertedDate)")
}