UTC时间记录在夏令时开始前的1点到1点59分重复两次 [英] UTC time record repeating 1:00 to 1:59 am twice, 5 hours before start of daylight saving

问题描述

UTC time record 5 hours before start of Spring Day Light Saving, displays 1:00 to 1:59 UTC time duration am twice. First, from 8:00 pm to 8:59 pm and then again from 9:00 pm to 9:59 pm. UTC time becomes normal 3:00 am again at local 10 pm time.

when local time goes to 8:59 pm to 9:00 pm on 11 March '17, UTC time goes back from 1:59 am to 1:00 am and since then continue to record time upto 1:59 am. And when local time goes to 9:59 pm to 10:00 pm same day, UTC time records goes to 1:59 am to 3:00 am. It all happening before start of Day light saving (5 hours before in UTC-5 time zone).

Summary:
local time duration ----------------- UTC time duration
(11th March '17) --------------------- (12th March '17)
8:00pm to 8:59 pm -------------- 1:00 am to 1:59 am
9:00pm to 9:59 pm -------------- 1:00 am to 1:59 am
10:00 pm onwards --------------- 3:00 am onwards

什么我试过了：

What I have tried:

double TimeCalculationClass :: GetUTCTime()
{
   struct tm*   starTime; 
   struct tm stmTime;
   time_t localTimestamp = (long)m_dTime;
   double dTime;
   SYSTEMTIME   sysTime, sysUTcST;
   FILETIME  locFileTime, utcFileTime;

   dTime = m_dTime;

   /* Convert to a SYSTEMTIME */
   sysTime.wSecond = (unsigned short)starTime->tm_sec;
   sysTime.wMinute = (unsigned short)starTime->tm_min;
   sysTime.wHour = (unsigned short)starTime->tm_hour;
   sysTime.wDay = (unsigned short)starTime->tm_mday;
   sysTime.wMonth = (unsigned short)(starTime->tm_mon + 1);
   sysTime.wYear = (unsigned short)(starTime->tm_year + 1900);
   sysTime.wMilliseconds = 0;

   /* convert to a local FileTime */
   SystemTimeToFileTime(&sysTime, &locFileTime);

   /* convert local filetime to a file time based on the Coordinated 
   Universal Time (UTC). */
   LocalFileTimeToFileTime(&locFileTime, &utcFileTime);

   /* convert utc filetime to utc system time */
   FileTimeToSystemTime(&utcFileTime, &sysUTcST);

   /* convert system time to struct tm */
   stmTime.tm_sec = sysUTcST.wSecond;
   stmTime.tm_min = sysUTcST.wMinute;
   stmTime.tm_hour = sysUTcST.wHour;
   stmTime.tm_mday = sysUTcST.wDay;
   stmTime.tm_mon = sysUTcST.wMonth - 1;
   stmTime.tm_year = sysUTcST.wYear - 1900;
   stmTime.tm_wday = sysUTcST.wDayOfWeek;
   stmTime.tm_yday = 0;
   stmTime.tm_isdst = -1;
   dTime = (double)mktime(&stmTime);

   //if (stTime.wMilliseconds != 0)
   dTime = dTime + ((double)sysTime.wMilliseconds / 1000);

   return dTime;
}

推荐答案

请参阅 SystemTimeToFileTime函数（Windows） [ ^ ]文档：

See the SystemTimeToFileTime function (Windows)[^] documentation:

Quote：

将系统时间转换为文件时间格式。系统时间基于协调世界时（UTC）。

Converts a system time to file time format. System time is based on Coordinated Universal Time (UTC).

和 SYSTEMTIME结构（Windows） [ ^ ]：

and SYSTEMTIME structure (Windows)[^]:

Quote：

时间是协调世界时（UTC）或本地时间，具体取决于被调用的函数。

The time is either in coordinated universal time (UTC) or local time, depending on the function that is being called.

您的代码创建本地 SYSTEMTIME 并将其传递给 SystemTimeToFileTime ，这需要UTC时间。您必须致电 TzSpecificLocalTimeToSystemTime函数（Windows） [ ^ ]首先。



处理时间的一般规则：

始终以UTC格式存储它们并执行所有计算（时间跨度） / duration）使用UTC时间。仅将本地时间用于用户交互（输入/输出）。

Your code creates a local SYSTEMTIME and passes that to SystemTimeToFileTime which requires an UTC time. You have to call TzSpecificLocalTimeToSystemTime function (Windows)[^] first.

The general rule for handling times:
Always store them in UTC and perform all calculations (time span / duration) using UTC times. Use local time only for user interaction (input / output).

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