POCO C++ 框架：日期時間處理

常用類與格式化

POCO 日期時間類內部實現簡潔，支援多種標準格式輸出。

代碼範例

#include <Poco/LocalDateTime.h>
#include <Poco/DateTime.h>
#include <Poco/DateTimeFormat.h>
#include <Poco/DateTimeFormatter.h>
#include <Poco/DateTimeParser.h>
#include <iostream>

using Poco::LocalDateTime;
using Poco::DateTime;
using Poco::DateTimeFormat;
using Poco::DateTimeFormatter;
using Poco::DateTimeParser;

int main() {
    LocalDateTime now;
    std::cout << "年：" << now.year() << std::endl;
    std::cout << "月：" << now.month() << std::endl;
    std::cout << "日：" << now.day() << std::endl;
    std::cout << "時：" << now.hour() << std::endl;
    std::cout << "分：" << now.minute() << std::endl;
    std::cout << "秒：" << now.second() << std::endl;
    std::cout << "本周第 " << now.dayOfWeek() << " 天" << std::endl;
    std::cout << "本年第 " << now.dayOfYear() << " 天" << std::endl;
    std::cout << "儒略日：" << now.julianDay() << std::endl;

    std::string iso = DateTimeFormatter::format(now, DateTimeFormat::ISO8601_FORMAT);
    std::cout << "ISO8601：" << iso << std::endl;
    std::string http = DateTimeFormatter::format(now, DateTimeFormat::HTTP_FORMAT);
    std::cout << "HTTP：" << http << std::endl;
    std::string asctime = DateTimeFormatter::format(now, DateTimeFormat::ASCTIME_FORMAT);
    std::cout << "ANSI C：" << asctime << std::endl;
    std::string sortable = DateTimeFormatter::format(now, DateTimeFormat::SORTABLE_FORMAT);
    std::cout << "可排序：" << sortable << std::endl;

    DateTime dt; int tzd;
    DateTimeParser::parse(DateTimeFormat::ISO8601_FORMAT, iso, dt, tzd);
    dt.makeUTC(tzd);
    LocalDateTime ldt(tzd, dt);
    return 0;
}

關鍵點

• LocalDateTime：本地時間，含時區偏移。
• DateTimeFormatter::format：多種預設格式（ISO8601、HTTP、ANSI C、可排序）。
• DateTimeParser::parse：字串解析為 DateTime，返回時區偏移。
• 歷史上儒略日、ISO8601 等標準演變有趣，可深入閱讀文檔。