import java.time.*;
import java.time.format.DateTimeFormatter;
import java.util.Date;
public class DateToUtcConverter {
    // 方法1：Date 轉(zhuǎn) UTC 字符串 (ISO 8601格式)
    public static String dateToUtcIso(Date date) {
        Instant instant = date.toInstant();
        return instant.toString(); // 自動(dòng)轉(zhuǎn)換為UTC時(shí)間
    }
    // 方法2：Date 轉(zhuǎn) UTC 字符串 (自定義格式)
    public static String dateToUtcFormatted(Date date, String pattern) {
        Instant instant = date.toInstant();
        return DateTimeFormatter.ofPattern(pattern)
                .withZone(ZoneOffset.UTC)
                .format(instant);
    }
    // 方法3：Date 轉(zhuǎn) UTC 時(shí)間戳
    public static long dateToUtcTimestamp(Date date) {
        return date.toInstant().toEpochMilli();
    }
    // 方法4：Date 轉(zhuǎn) ZonedDateTime (UTC)
    public static ZonedDateTime dateToUtcZonedDateTime(Date date) {
        return date.toInstant().atZone(ZoneOffset.UTC);
    }
}

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class LegacyDateConverter {
    public static String dateToUtcSimple(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        return sdf.format(date);
    }
}

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.text.SimpleDateFormat;
public class UtcConverterTool {
    public static void main(String[] args) {
        // 創(chuàng)建當(dāng)前時(shí)間對(duì)象
        Date now = new Date();
        System.out.println("本地時(shí)間: " + now);
        // 轉(zhuǎn)換為各種UTC格式
        System.out.println("\n===== Java 8 方式轉(zhuǎn)換 =====");
        System.out.println("UTC ISO 格式: " + toUtcIso(now));
        System.out.println("UTC 自定義格式: " + toUtcFormatted(now, "yyyy-MM-dd HH:mm:ss"));
        System.out.println("UTC 時(shí)間戳: " + toUtcTimestamp(now));
        System.out.println("UTC ZonedDateTime: " + toUtcZonedDateTime(now));
        System.out.println("\n===== 傳統(tǒng)方式轉(zhuǎn)換 =====");
        System.out.println("SimpleDateFormat UTC: " + toUtcSimple(now));
        System.out.println("Calendar UTC: " + toUtcWithCalendar(now));
    }
    // ===== Java 8 現(xiàn)代API =====
    /**
     * 轉(zhuǎn)換為UTC ISO格式 (e.g., 2023-08-15T12:30:45.123Z)
     */
    public static String toUtcIso(Date date) {
        return date.toInstant().toString();
    }
    /**
     * 自定義格式的UTC時(shí)間
     * @param pattern 格式如 "yyyy-MM-dd HH:mm:ss"
     */
    public static String toUtcFormatted(Date date, String pattern) {
        return DateTimeFormatter.ofPattern(pattern)
                .withZone(ZoneOffset.UTC)
                .format(date.toInstant());
    }
    /**
     * 獲取UTC時(shí)間戳（毫秒）
     */
    public static long toUtcTimestamp(Date date) {
        return date.toInstant().toEpochMilli();
    }
    /**
     * 轉(zhuǎn)換為UTC時(shí)區(qū)的ZonedDateTime對(duì)象
     */
    public static ZonedDateTime toUtcZonedDateTime(Date date) {
        return date.toInstant().atZone(ZoneOffset.UTC);
    }
    // ===== 傳統(tǒng)轉(zhuǎn)換方法 =====
    /**
     * 使用SimpleDateFormat轉(zhuǎn)換
     */
    public static String toUtcSimple(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        return sdf.format(date);
    }
    /**
     * 使用Calendar轉(zhuǎn)換
     */
    public static String toUtcWithCalendar(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        // 轉(zhuǎn)換為UTC時(shí)間
        calendar.setTimeZone(TimeZone.getTimeZone("UTC"));
        return String.format("%04d-%02d-%02d %02d:%02d:%02d",
            calendar.get(Calendar.YEAR),
            calendar.get(Calendar.MONTH) + 1,
            calendar.get(Calendar.DAY_OF_MONTH),
            calendar.get(Calendar.HOUR_OF_DAY),
            calendar.get(Calendar.MINUTE),
            calendar.get(Calendar.SECOND));
    }
    // ===== 實(shí)用工具方法 =====
    /**
     * 獲取當(dāng)前UTC時(shí)間字符串
     */
    public static String currentUtcIso() {
        return Instant.now().toString();
    }
    /**
     * 獲取當(dāng)前UTC時(shí)間對(duì)象
     */
    public static Date currentUtcDate() {
        return Date.from(Instant.now());
    }
    /**
     * 時(shí)區(qū)轉(zhuǎn)換工具
     * @param date 原始時(shí)間
     * @param fromZone 原始時(shí)區(qū)ID (e.g., "Asia/Shanghai")
     * @param toZone 目標(biāo)時(shí)區(qū)ID (e.g., "UTC")
     */
    public static Date convertBetweenTimeZones(Date date, String fromZone, String toZone) {
        ZonedDateTime fromZoned = date.toInstant()
                .atZone(ZoneId.of(fromZone));
        ZonedDateTime toZoned = fromZoned.withZoneSameInstant(ZoneId.of(toZone));
        return Date.from(toZoned.toInstant());
    }
}

本地時(shí)間: Tue Aug 15 20:45:30 CST 2023
===== Java 8 方式轉(zhuǎn)換 =====
UTC ISO 格式: 2023-08-15T12:45:30.456Z
UTC 自定義格式: 2023-08-15 12:45:30
UTC 時(shí)間戳: 1692103530456
UTC ZonedDateTime: 2023-08-15T12:45:30.456Z
===== 傳統(tǒng)方式轉(zhuǎn)換 =====
SimpleDateFormat UTC: 2023-08-15T12:45:30.456Z
Calendar UTC: 2023-08-15 12:45:30

2023-08-15T12:30:45.123Z

// 明確指定時(shí)區(qū)
ZonedDateTime utcTime = ZonedDateTime.now(ZoneOffset.UTC);
// 避免隱式使用系統(tǒng)默認(rèn)時(shí)區(qū)
ZonedDateTime riskyTime = ZonedDateTime.now(); // 可能產(chǎn)生意外結(jié)果

public ZonedDateTime parseUserInput(String input, String userTimeZone) {
    LocalDateTime localDateTime = LocalDateTime.parse(input, 
        DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
    return localDateTime.atZone(ZoneId.of(userTimeZone));
}

// 上海時(shí)間轉(zhuǎn)UTC
ZonedDateTime shanghaiTime = ZonedDateTime.now(ZoneId.of("Asia/Shanghai"));
Instant utcInstant = shanghaiTime.toInstant();

DateTimeFormatter strictFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd")
    .withResolverStyle(ResolverStyle.STRICT);

// 發(fā)送到后端
const utcString = new Date().toISOString(); 

Instant instant = Instant.parse(utcString);

ZonedDateTime londonTime = ZonedDateTime.now(ZoneId.of("Europe/London"));