C/C++标准库之转换UTC时间到local本地时间详解

// test_datetime_format.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <time.h>
#include <sstream>
#include <iostream>
#include <assert.h>

//2014-09-13T10:52:36Z
//2014-09-13 10:52:36
char* ConvertUtcToLocalTime(struct tm* t2,const char* date){

 struct tm t;
 memset(&t,0,sizeof(t));
 t.tm_year = atoi(date)-1900;
 t.tm_mon = atoi(date+5)-1;
 t.tm_mday = atoi(date+8);
 t.tm_hour = atoi(date+11);
 t.tm_min = atoi(date+14);
 t.tm_sec = atoi(date+17);

 time_t tt = _mkgmtime64(&t);
 if(tt != -1){
 if(t2 == NULL){
  t2 = &t; 
 }
 *t2 = *localtime(&tt);
 char* ds = (char*) malloc(24);
 memset(ds, 0, 24);
 sprintf(ds, "%.4d-%.2d-%.2d %.2d:%.2d:%.2d", t2->tm_year + 1900,
  t2->tm_mon + 1, t2->tm_mday, t2->tm_hour, t2->tm_min,
  t2->tm_sec);
 return ds;
 }
 return NULL;
}


//https://www.w3.org/TR/NOTE-datetime
//https://msdn.microsoft.com/en-us/library/2093ets1.aspx
//2014-09-13T10:52:36Z
int _tmain(int argc, _TCHAR* argv[])
{
 const char* kTime = "2014-09-13 18:52:36";
 std::cout << "Source DateTime: " << "2014-09-13T10:52:36Z" << std::endl;
 auto t = ConvertUtcToLocalTime(NULL,"2014-09-13T10:52:36Z");
 std::cout << "Dest DateTime: " << t << std::endl;
 assert(!strcmp(t,kTime));

 t = ConvertUtcToLocalTime(NULL,"2014-09-13 10:52:36");
 std::cout << t << std::endl;
 assert(!strcmp(t,kTime));

 struct tm tt;
 t = ConvertUtcToLocalTime(&tt,"2014-09-13 10:52:36");
 std::cout << t << std::endl;
 assert(!strcmp(t,kTime));
 assert(tt.tm_year == (2014-1900));
 assert(tt.tm_mon == 9-1);
 assert(tt.tm_mday == 13);
 assert(tt.tm_hour == 18);
 assert(tt.tm_min == 52);
 assert(tt.tm_sec == 36);

 return 0;
}


}

Source DateTime: 2014-09-13T10:52:36Z
Dest DateTime: 2014-09-13 18:52:36
2014-09-13 18:52:36
2014-09-13 18:52:36

#ifndef UTC_TIME_STAMP_H_
#define UTC_TIME_STAMP_H_

#include <windows.h>
#include <sys/timeb.h>
#include <time.h> 

#if !defined(_WINSOCK2API_) && !defined(_WINSOCKAPI_)
struct timeval
{
long tv_sec;
long tv_usec;
};
#endif

static int gettimeofday(struct timeval* tv)
{
 union {
    long long ns100;
    FILETIME ft;
 } now;
 GetSystemTimeAsFileTime (&now.ft);
 tv->tv_usec = (long) ((now.ns100 / 10LL) % 1000000LL);
 tv->tv_sec = (long) ((now.ns100 - 116444736000000000LL) / 10000000LL);

 return (0);
}
//获取1970年至今UTC的微妙数
static time_t TimeConversion::GetUtcCaressing()
{
 timeval tv;
 gettimeofday(&tv); 
 return ((time_t)tv.tv_sec*(time_t)1000000+tv.tv_usec);
}
#endif

timeval tv;
gettimeofday(&tv); 

time_t timep;
struct tm *p;
time(&timep);
p=localtime(&timep);
timep = mktime(p);
printf("%d\n",timep);