如何获取当前时区？ [英] How to get the current time zone?

问题描述

在大多数我见过的例子：

In most of the examples I had seen:

time_zone_ptr zone( new posix_time_zone("MST-07") ); 

但我只是想获得当前时区为运行code机器。我不想硬code中的时区名称。

But I just want to get the current time zone for the machine that runs the code. I do not want to hard code the time zone name.

推荐答案

普通POSIX：的调用tzset，使用TZNAME 。

#include <ctime>
tzset();
time_zone_ptr zone(new posix_time_zone(tzname[localtime(0)->tm_isdst]));

Posix的使用的glibc / BSD 补充：

time_zone_ptr zone(new posix_time_zone(localtime(0)->tm_zone));

---

以上的缩写的Posix时区，定义方面UTC的偏移量，并随着时间的推移（有一个更长的形式可以包括DST的过渡，而不是政治和历史变迁）。

---

The above are abbreviated Posix timezones, defined in terms of offset from UTC and not stable over time (there's a longer form that can include DST transitions, but not political and historical transitions).

ICU 是便携和具有逻辑检索系统时区为奥尔森时区（由 sumwale 片段）：

ICU is portable and has logic for retrieving the system timezone as an Olson timezone (snippet by sumwale):

// Link with LDLIBS=`pkg-config icu-i18n --libs`
#include <unicode/timezone.h>
#include <iostream>

using namespace U_ICU_NAMESPACE;

int main() {
  TimeZone* tz = TimeZone::createDefault();
  UnicodeString us;
  std::string s;

  tz->getID(us);
  us.toUTF8String(s);
  std::cout << "Current timezone ID: " << s << '\n';
  delete tz;
}

在Linux中，ICU实施要与tzset兼容和和 TZ http://freedesktop.org/software/systemd/man /localtime.html相对=nofollow> 的/ etc /本地时间 ，其中最近的Linux系统是specced是包含奥尔森标识一个符号链接（< A HREF =htt​​p://stackoverflow.com/a/28069672/229753>这里的记录）。参见 uprv_tzname 的实施细节。

On Linux, ICU is implemented to be compatible with tzset and looks at TZ and /etc/localtime, which on recent Linux systems is specced to be a symlink containing the Olson identifier (here's the history). See uprv_tzname for implementation details.

升压不知道如何使用奥尔森标识符。你可以建立一个的posix_time_zon​​e 使用非DST和DST偏移，但在这一点上，最好使用ICU执行，以保持。见<一href=\"http://www.boost.org/doc/libs/1_57_0/libs/locale/doc/html/dates_times_timezones.html#dates_times_timezones_qna\"相对=nofollow>这个升压常见问题解答。

Boost doesn't know how to use the Olson identifier. You could build a posix_time_zone using the non-DST and DST offsets, but at this point, it's best to keep using the ICU implementation. See this Boost FAQ.

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