int nTime = time(NULL);//得到當前系統時間int nDays = nTime/DAYMS + 1;//time函數獲取的是從1970年以來的毫秒數，因此需要先得到天數int nYear4 = nDays/FOURYEARS;//得到從1970年以來的周期（4年）的次數int nRemain = nDays%FOURYEARS;//得到不足一個周期的天數int nDesYear = 1970 + nYear4*4;int nDesMonth = 0, nDesDay = 0;bool bLeapYear = false;if ( nRemain<365 )//一個周期內，第一年{//平年}else if ( nRemain<(365+365) )//一個周期內，第二年{//平年nDesYear += 1;nRemain -= 365;}else if ( nRemain<(365+365+365) )//一個周期內，第三年{//平年nDesYear += 2;nRemain -= (365+365);}else//一個周期內，第四年，這一年是閏年{//潤年nDesYear += 3;nRemain -= (365+365+365);bLeapYear = true;}GetMonthAndDay(nRemain, nDesMonth, nDesDay, bLeapYear);

static const int MON1[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};	//平年static const int MON2[12] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};	//閏年static const int FOURYEARS = (366 + 365 +365 +365);	//每個四年的總天數static const int DAYMS = 24*3600;	//每天的毫秒數void GetMonthAndDay(int nDays, int& nMonth, int& nDay, bool IsLeapYear){	int *pMonths = IsLeapYear?MON2:MON1;	//循環減去12個月中每個月的天數，直到剩余天數小于等于0，就找到了對應的月份	for ( int i=0; i<12; ++i )	{		int nTemp = nDays - pMonths[i];		if ( nTemp<=0 )		{			nMonth = i+1;			if ( nTemp == 0 )//表示剛好是這個月的最后一天，那么天數就是這個月的總天數了				nDay = pMonths[i];			else				nDay = nDays;			break;		}		nDays = nTemp;	}}

<pre name="code" class="cpp">/****errno_t _gmtime32_s(ptm, timp) - convert *timp to a structure (UTC)**Purpose:*    Converts the calendar time value, in 32 bit internal format, to*    broken-down time (tm structure) with the corresponding UTC time.**Entry:*    const time_t *timp - pointer to time_t value to convert**Exit:*    errno_t = 0 success* tm members filled-in*    errno_t = non zero* tm members initialized to -1 if ptm != NULL**Exceptions:********************************************************************************/errno_t __cdecl _gmtime32_s (struct tm *ptm,const __time32_t *timp){__time32_t caltim;/* = *timp; *//* calendar time to convert */int islpyr = 0; /* is-current-year-a-leap-year flag */REG1 int tmptim;REG3 int *mdays;/* pointer to days or lpdays */struct tm *ptb = ptm;_VALIDATE_RETURN_ERRCODE( ( ptm != NULL ), EINVAL )memset( ptm, 0xff, sizeof( struct tm ) );_VALIDATE_RETURN_ERRCODE( ( timp != NULL ), EINVAL )caltim = *timp;_VALIDATE_RETURN_ERRCODE_NOEXC( ( caltim >= _MIN_LOCAL_TIME ), EINVAL )/* * Determine years since 1970. First, identify the four-year interval * since this makes handling leap-years easy (note that 2000 IS a * leap year and 2100 is out-of-range). */tmptim = (int)(caltim / _FOUR_YEAR_SEC);caltim -= ((__time32_t)tmptim * _FOUR_YEAR_SEC);/* * Determine which year of the interval */tmptim = (tmptim * 4) + 70; /* 1970, 1974, 1978,...,etc. */if ( caltim >= _YEAR_SEC ) {  tmptim++;    /* 1971, 1975, 1979,...,etc. */  caltim -= _YEAR_SEC;  if ( caltim >= _YEAR_SEC ) {tmptim++;  /* 1972, 1976, 1980,...,etc. */caltim -= _YEAR_SEC;/* * Note, it takes 366 days-worth of seconds to get past a leap * year. */if ( caltim >= (_YEAR_SEC + _DAY_SEC) ) {tmptim++;  /* 1973, 1977, 1981,...,etc. */caltim -= (_YEAR_SEC + _DAY_SEC);}else {/* * In a leap year after all, set the flag. */islpyr++;}  }}/* * tmptim now holds the value for tm_year. caltim now holds the * number of elapsed seconds since the beginning of that year. */ptb->tm_year = tmptim;/* * Determine days since January 1 (0 - 365). This is the tm_yday value. * Leave caltim with number of elapsed seconds in that day. */ptb->tm_yday = (int)(caltim / _DAY_SEC);caltim -= (__time32_t)(ptb->tm_yday) * _DAY_SEC;/* * Determine months since January (0 - 11) and day of month (1 - 31) */if ( islpyr )  mdays = _lpdays;else  mdays = _days;for ( tmptim = 1 ; mdays[tmptim] < ptb->tm_yday ; tmptim++ ) ;ptb->tm_mon = --tmptim;ptb->tm_mday = ptb->tm_yday - mdays[tmptim];/* * Determine days since Sunday (0 - 6) */ptb->tm_wday = ((int)(*timp / _DAY_SEC) + _BASE_DOW) % 7;/* * Determine hours since midnight (0 - 23), minutes after the hour * (0 - 59), and seconds after the minute (0 - 59). */ptb->tm_hour = (int)(caltim / 3600);caltim -= (__time32_t)ptb->tm_hour * 3600L;ptb->tm_min = (int)(caltim / 60);ptb->tm_sec = (int)(caltim - (ptb->tm_min) * 60);ptb->tm_isdst = 0;return 0;}