关于c ++：将boost ptime从本地时间转换为UTC

Convert boost ptime from local time to UTC

我有一个boost::posix_time::ptime对象(Boost v1.60)，它在系统的时区中有日期和时间信息。我需要将其转换为UTC的unix时间戳。

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time_t convertLocalPtimeToTimestamp(const boost::posix_time::ptime& pt)
{
using namespace boost::local_time;
static const time_t t_null = 0;
static struct tm* tm_local = localtime(&t_null);
static time_zone_ptr zone(new posix_time_zone(tm_local->tm_zone));
LOG(debug) <<"Zone" << zone->to_posix_string();

local_date_time az(pt.date(), pt.time_of_day(), zone, local_date_time::EXCEPTION_ON_ERROR);
LOG(debug) <<"local_date_time:" << az;
LOG(debug) <<"local_time:" << az.local_time();
LOG(debug) <<"utc_time:" << az.utc_time();
struct tm t = to_tm(az);
time_t ts = mktime(&t);

return ts;
}

我的案例(欧洲/马德里)的结果是：

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Zone CET+00
local_date_time: 2016-Oct-05 17:36:27.701162 CET
local_time: 2016-Oct-05 17:36:27.701162
utc_time: 2016-Oct-05 17:36:27.701162
1475685387

此结果中存在各种错误：

应将时区检测为夏令时：CEST(+0200)不是CET(+0100)
即使没有DST检测，utc_time也应该与local_time不同。
最后，时间戳应代表UTC时间，而不是本地时间。

任何帮助，将不胜感激。

相关讨论

这是我要解决的问题的Boost实现。

我不想使用另一个第三方库，我在Windows中遇到jgaida的答案(tm_zone和tm_gmtoff不是tm的成员)。

我通过多次更改Windows 10 PC中的时区来测试此代码。

边缘情况"(UTC-12：00)国际日期线西"和"(UTC + 14:00)Kiritimati岛"也进行了测试，结果是成功的。

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time_t convertLocalPtimeToTimestamp (const boost::posix_time::ptime& pt)
{
using namespace boost::posix_time;
using namespace boost::local_time;

_tzset (); // This is needed if the time zone changes after the program starts.

// Grab copies of the current time in local and UTC form.
auto p_time = microsec_clock::universal_time (); // UTC.
auto lp_time = boost::date_time::c_local_adjustor<ptime>::utc_to_local (p_time);

// Calculate the difference between the UTC and local time and put it in a string.
// This will yield"-07:00:00" for PST and"-08:00:00" for PDT.
auto time_diff = to_simple_string (lp_time - p_time);

// Convert the ptime to a local_date_time object using the local time zone.
// We will create the time zone with the time difference string generated above.
local_date_time local_time (p_time, time_zone_ptr (new posix_time_zone (time_diff)));

// Calculate the difference in milliseconds between the UTC and local time.
auto time_t_diff = to_time_t (p_time) - to_time_t (local_time.local_time ());

// Return the given time in ms plus the time_t difference (to get the UTC ms).
return to_time_t (pt) + time_t_diff;
}

相关讨论

Fwiw，来自这个免费的开源库：

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#include"chrono_io.h"
#include"tz.h"
#include <iostream>

int
main()
{
using namespace date;
using namespace std::chrono;
auto az = make_zoned("Europe/Madrid",
local_days{2016_y/oct/5} + 17h + 36min + 27s + 701162us);
std::cout <<"Zone" << az.get_time_zone()->name() << '
';
std::cout <<"local_date_time:" << az << '
';
std::cout <<"local_time: " << az.get_local_time() << '
';
std::cout <<"utc_time: " << az.get_sys_time() << '
';
std::cout << floor<seconds>(az.get_sys_time()).time_since_epoch() << '
';
}

输出是：

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Zone Europe/Madrid
local_date_time: 2016-10-05 17:36:27.701162 CEST
local_time: 2016-10-05 17:36:27.701162
utc_time: 2016-10-05 15:36:27.701162
1475681787s

也可以使用current_zone()构造zoned_time，如下所示：

1 2	auto az = make_zoned(current_zone(), local_days{2016_y/oct/5} + 17h + 36min + 27s + 701162us);

要么：

1	auto az = make_zoned(current_zone(), system_clock::now());