移动开发中的日期和时间：概念、格式及处理方法

import Foundation

// 缓存的 DateFormatter — 创建一次
private let dateFormatter: DateFormatter = {
    let formatter = DateFormatter()
    formatter.dateFormat = "dd.MM.yyyy HH:mm"
    formatter.locale = Locale(identifier: "ru_RU")
    formatter.timeZone = TimeZone(identifier: "Europe/Moscow")
    return formatter
}()

// ISO8601DateFormatter — 轻量级替代方案
private let isoFormatter: ISO8601DateFormatter = {
    let formatter = ISO8601DateFormatter()
    formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
    return formatter
}()

let now = Date()
let formattedDate = dateFormatter.string(from: now)
// "01.07.2026 14:30"
let isoDate = isoFormatter.string(from: now)
// "2026-07-01T14:30:00.000Z"

import java.time.LocalDate
import java.time.LocalDateTime
import java.time.ZonedDateTime
import java.time.format.DateTimeFormatter
import java.time.ZoneId

// 创建和格式化当前日期
val today = LocalDate.now()
val formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy")
val formatted = today.format(formatter)

// 处理时区
val utcTime = ZonedDateTime.now(ZoneId.of("UTC"))
val moscowTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/Moscow"))

import Foundation

// UTC 到本地时间的转换（iOS）
func formatToLocalTime(utcDate: Date, timeZoneId: String) -> String {
    let formatter = DateFormatter()
    formatter.dateFormat = "dd.MM.yyyy HH:mm"
    formatter.timeZone = TimeZone(identifier: timeZoneId)
    return formatter.string(from: utcDate)
}

// 确定设备时区
let localTimeZone = TimeZone.current
let isDST = localTimeZone.isDaylightSavingTime()
let secondsFromGMT = localTimeZone.secondsFromGMT()

import java.time.Instant
import java.time.ZonedDateTime
import java.time.ZoneId

// 将 Unix Timestamp 转换为本地时间
fun toLocalDisplay(unixSeconds: Long): String {
    val instant = Instant.ofEpochSecond(unixSeconds)
    val local = instant.atZone(ZoneId.systemDefault())
    return local.format(DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm"))
}

import org.threeten.bp.LocalDate
import org.threeten.bp.format.DateTimeFormatter

// 在 Application 中初始化
class App : Application() {
    override fun onCreate() {
        super.onCreate()
        AndroidThreeTen.init(this)
    }
}

// API 与 java.time 相同
val today = LocalDate.now()
val formatted = today.format(DateTimeFormatter.ISO_LOCAL_DATE)

import Foundation

// 在 iOS 上获取 Unix Timestamp
let seconds = Date().timeIntervalSince1970
let milliseconds = Int64(seconds * 1000)

// 通过 TrueTime 进行 NTP 同步
TrueTime.shared.start { result in
    switch result {
    case .success:
        let ntpTime = TrueTime.shared.now()
        print("精确时间：\(ntpTime)")
    case .failure(let error):
        print("NTP 错误：\(error)")
    }
}