struct tm { 
    int tm_sec;   /* seconds after the minute - [0,59] */ 
    int tm_min;   /* minutes after the hour - [0,59] */ 
    int tm_hour;  /* hours since midnight - [0,23] */ 
    int tm_mday;  /* day of the month - [1,31] */ 
    int tm_mon;   /* months since January - [0,11] */ 
    int tm_year;  /* years since 1900 */ 
    int tm_wday;  /* days since Sunday - [0,6] */ 
    int tm_yday;  /* days since January 1 - [0,365] */ 
    int tm_isdst;  /* daylight savings time flag */ 
    }; 

struct timeval {
     time_t    tv_sec;   /* seconds */
     suseconds_t  tv_usec; /* microseconds */
 };

time_t time(time_t *t); //取得從1970年1月1日至今的秒數(shù) 

char *asctime(const struct tm *tm); //將結(jié)構(gòu)中的信息轉(zhuǎn)換為真實世界的時間，以字符串的形式顯示 

char *ctime(const time_t *timep); //將timep轉(zhuǎn)換為真是世界的時間，以字符串顯示，它和asctime不同就在于傳入的參數(shù)形式不一樣 

struct tm *gmtime(const time_t *timep); //將time_t表示的時間轉(zhuǎn)換為沒有經(jīng)過時區(qū)轉(zhuǎn)換的UTC時間，是一個struct tm結(jié)構(gòu)指針  

struct tm *localtime(const time_t *timep); //和gmtime類似，但是它是經(jīng)過時區(qū)轉(zhuǎn)換的時間。 

time_t mktime(struct tm *tm); //將struct tm 結(jié)構(gòu)的時間轉(zhuǎn)換為從1970年至今的秒數(shù) 

int gettimeofday(struct timeval *tv, struct timezone *tz); //返回當(dāng)前距離1970年的秒數(shù)和微妙數(shù)，后面的tz是時區(qū)，一般不用 

double difftime(time_t time1, time_t time2); //返回兩個時間相差的秒數(shù) 

time_t t; //秒時間 
tm* local; //本地時間  
tm* gmt;  //格林威治時間 
char buf[128]= {0}; 
 
t = time(NULL); //或者time(&t);//獲取目前秒時間 
local = localtime(&t); //轉(zhuǎn)為本地時間 
strftime(buf, 64, "%Y-%m-%d %H:%M:%S", local); 
std::cout << buf << std::endl; 
 
gmt = gmtime(&t);//轉(zhuǎn)為格林威治時間 
strftime(buf, 64, "%Y-%m-%d %H:%M:%S", gmt); 
std::cout << buf << std::endl; 

 
tm tm_; 
time_t t_; 
char buf[128]= {0}; 
 
strcpy(buf, "2012-01-01 14:00:00"); 
strptime(buf, "%Y-%m-%d %H:%M:%S", &tm_); //將字符串轉(zhuǎn)換為tm時間 
tm_.tm_isdst = -1; 
t_ = mktime(&tm_); //將tm時間轉(zhuǎn)換為秒時間 
t_ += 3600; //秒數(shù)加3600 
 
tm_ = *localtime(&t_);//輸出時間 
strftime(buf, 64, "%Y-%m-%d %H:%M:%S", &tm_); 
std::cout << buf << std::endl; 
 

time_t StringToDatetime(char *str) 
{ 
  tm tm_; 
  int year, month, day, hour, minute,second; 
  sscanf(str,"%d-%d-%d %d:%d:%d", &year, &month, &day, &hour, &minute, &second); 
  tm_.tm_year = year-1900; 
  tm_.tm_mon  = month-1; 
  tm_.tm_mday = day; 
  tm_.tm_hour = hour; 
  tm_.tm_min  = minute; 
  tm_.tm_sec  = second; 
  tm_.tm_isdst = 0; 
 
  time_t t_ = mktime(&tm_); //已經(jīng)減了8個時區(qū) 
  return t_; //秒時間 
} 

struct timeval start_time, over_time, consume_time;
gettimeofday(&over_time, NULL);//get the current time
start_time = over_time;
 do something.....
gettimeofday(&over_time, NULL);

timeval_subtract(&consume_time, &start_time, &over_time);//計算時間差104./** 
   * 計算兩個時間的間隔，得到時間差 
   * @param struct timeval* resule 返回計算出來的時間 
   * @param struct timeval* x 需要計算的前一個時間 
   * @param struct timeval* y 需要計算的后一個時間 
   * return -1 failure ,0 success 
 **/ 
timeval_subtract(struct timeval* result, struct timeval* x, struct timeval* y) 
 { 
    if ( x->tv_sec>y->tv_sec ) 
         return -1; 
  
    if ( (x->tv_sec==y->tv_sec) && (x->tv_usec>y->tv_usec) ) 
         return -1; 
  
    result->tv_sec = ( y->tv_sec-x->tv_sec ); 
    result->tv_usec = ( y->tv_usec-x->tv_usec ); 
  
    if (result->tv_usec<0) 
    { 
         result->tv_sec--; 
         result->tv_usec+=1000000; 
    } 
  
    return 0; 
 }