如何获取当前UTC偏移量（时区）？ [英] How do I get the current UTC offset (time zone)?

问题描述

如何获得当前UTC偏移量（如时区，但只是UTC偏移量的当前时刻）？

How do I get the current UTC offset (as in time zone, but just the UTC offset of the current moment)?

我需要一个答案像+ 02:00。

I need an answer like "+02:00".

推荐答案

此问题有两部分：

1. 获取UTC偏移量为 boost :: posix_time :: time_duration


2. code> time_duration 如指定

1. Get the UTC offset as a boost::posix_time::time_duration
2. Format the time_duration as specified

---

，获得本地时区在广泛实现的API中不是很好地暴露。然而，我们可以通过取相对于UTC的时刻和相对于当前时区的相同时刻的差异来获得它，例如：

---

Apparently, getting the local time zone is not exposed very well in a widely implemented API. We can, however, get it by taking the difference of a moment relative to UTC and the same moment relative to the current time zone, like this:

boost::posix_time::time_duration get_utc_offset() {
    using namespace boost::posix_time;

    // boost::date_time::c_local_adjustor uses the C-API to adjust a
    // moment given in utc to the same moment in the local time zone.
    typedef boost::date_time::c_local_adjustor<ptime> local_adj;

    const ptime utc_now = second_clock::universal_time();
    const ptime now = local_adj::utc_to_local(utc_now);

    return now - utc_now;
}

---

格式化指定的偏移只是一个充满正确的问题 time_facet ：

std::string get_utc_offset_string() {
    std::stringstream out;

    using namespace boost::posix_time;
    time_facet* tf = new time_facet();
    tf->time_duration_format("%+%H:%M");
    out.imbue(std::locale(out.getloc(), tf));

    out << get_utc_offset();

    return out.str();
}

现在， get_utc_offset_string c>将产生所需的结果。

Now, get_utc_offset_string() will yield the desired result.

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