C语言 日期型转double型

 

在C语言中没有直接将日期转换为double型的函数，但是在将日期类型保存到文件时往往需要日期的转换。 
/* ************************************************************************************************************
* conversion between double type and datetime type　　　　　　　　　　　　　　　　　　　　　　
* wxz 2011-08-29 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
* Compiled by VC6.0and VC2010 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
**************************************************************************************************************/

/**********************************************
 * EncodeDateTime.h                                     
 **********************************************/
#ifndef EncodeDateTime_H
#define  EncodeDateTime_H
 typedef unsigned short word;//unsigned two bytes
//convert datetime to double type
 extern double EncodeDateTime(word year,word month,word day,word hour,word min,word sec,word msec); //convert double to datetime type
 extern void DecodeDateTime(double dt,word *year,word *month,word *day,word *hour,word *min,word *sec,word *msec);
 //extern char *DecodeDateTime(char* dtStr,  double dt,word *year,word *month,word *day,word *hour,word *min,word *sec,word *msec);
#endif
/* ********************************************************
* conversion between double type and datetime type         
* EncodeDateTime.c                                       
***********************************************************/
#include <stdio.h>
#include "EncodeDateTime.h"

const int DateDelta = 693594;// Days between 1/1/0001 and 12/31/1899
const int HoursPerDay   = 24;//hours per day
const int MinsPerHour   = 60;//minutes per hour
const int SecsPerMin    = 60;//seconds per minute
const int MSecsPerSec   = 1000;//milliseconds per second
const double MinDateTime= -657434.0;       // 01/01/0100 12:00:00.000 AM
const double MaxDateTime=  2958465.99999; // 12/31/9999 11:59:59.999 PM

void DivMod(int dividend,int divisor,word *result,word *remainder)
{
 *result=dividend/divisor;
 *remainder=dividend%divisor;
}

//convert datetime to double type
double EncodeDateTime(word year,word month,word day,word hour,word min,word sec,word msec)
{
 const int MinsPerDay    = HoursPerDay * MinsPerHour;//minutes per day
 const int SecsPerDay    = MinsPerDay * SecsPerMin; //seconds per day
 const int SecsPerHour   = SecsPerMin * MinsPerHour; //seconds per hour
 const int MSecsPerDay   = SecsPerDay * MSecsPerSec; //milliseconds per day
 //
 int i;
 int days[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
 double date;
 double time;
 date=0;
 time=0;
 if ((year >= 1) && (year <= 9999) && (month >= 1) && (month <= 12))
 {
  //leap year
  if ((year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0))) days[2]=29;
  if ((day >= 1) && (day <= days[month]))
  {
   for( i=1;i<=month-1;i++) day+=days[i];
   year-=1;
   date= year * 365 + year / 4 - year / 100 + year / 400 + day - DateDelta;
   if ((hour < HoursPerDay) && (min < MinsPerHour) && (sec < SecsPerMin) && (msec < MSecsPerSec))
   {
     time = (hour * (MinsPerHour * SecsPerMin * MSecsPerSec) +
     min * (SecsPerMin * MSecsPerSec) +
     sec * MSecsPerSec +
     msec);
     time/=MSecsPerDay;
   }
   return date+time;  
  }
 }
 return 1; // 12/31/1899
}
//convert double to datetime type
void DecodeDateTime(double dt,word *year,word *month,word *day,word *hour,word *min,word *sec,word *msec)
{
 const int MinsPerDay    = HoursPerDay * MinsPerHour;//minutes per day
 const int SecsPerDay    = MinsPerDay * SecsPerMin; //seconds per day
 const int SecsPerHour   = SecsPerMin * MinsPerHour; //seconds per hour
 const int MSecsPerDay   = SecsPerDay * MSecsPerSec; //milliseconds per day

 const int D1 = 365;
 const int D4 = D1 * 4 + 1;
 const int D100 = D4 * 25 - 1;
 const int D400 = D100 * 4 + 1;
    //
 word y,m,d,r,temp;
 word hh,mm,ss,mss;
    char str[20]; //
 int ipart;//integer part
 double fpart;//float part
 int date,time; //date and time
 //int MinCount, MSecCount;
 word MinCount, MSecCount;
 int days[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
 ipart=0;
 fpart=0;
 y=0;m=0;d=0;r=0,temp=0;
 hh=0;mm=0;ss=0;mss=0;
 MinCount=0;
 MSecCount=0;
  if(!(dt< MinDateTime)||(dt >(int)MaxDateTime+1.0))
 {
   ipart=(int)(dt);
  fpart=dt-ipart;
  date=ipart+DateDelta;
  time=(int)(MSecsPerDay*fpart);
  //-------------------------decode date-------------------------
  if (date<=0)
  {
   *year=1899;
   *month=12;
   *day=31;
   *hour=0;
   *min=0;
   *sec=0;
   *msec=0;
  }
  else
  {
   temp=date % 7 +1;
   date-=1;
   y=1;
   while(date >= D400)
   {
    date-=D400;
    y+=400;
   }
   DivMod(date,D100,&r,&d);
   if (r==4)
   {
    r-=1;
    d+=D100;
   }
            y+=r*100;
   DivMod(d, D4, &r,&d);
   y+=r*4;
   DivMod(d,D1,&r,&d);
   if (r==4)
   {
    r-=1;
    d+=D1;
   }
   y+=r;
   //leap year
   if ((y % 4 == 0) && ((y % 100 != 0) || (y % 400 == 0))) days[2]=29;
   m = 1;
   while(1)
   {
    r=days[m];
    if (d< r) break;
    d-=r;
    m+=1;
   }
   *year = y;
   *month = m;
   *day = d + 1;
  }
  //-------------decode time----------------------------------------
  DivMod(time, SecsPerMin * MSecsPerSec, &MinCount, &MSecCount);
  DivMod(MinCount, MinsPerHour, &hh, &mm);
  DivMod(MSecCount, MSecsPerSec, &ss, &mss);
  *hour=hh;
  *min=mm;
  *sec=ss;
  *msec=mss;
 }
 
}

/* ********************************************************
* Test.c                                                                                  
**********************************************************/
#include "EncodeDateTime.h"
#include <stdio.h>
int main()
{
 word year,month,day,hour,min,sec,msec;
 double dt;
 char str[20];
 dt=EncodeDateTime(2011,8,29,16,21,40,0);
 DecodeDateTime(dt,&year,&month,&day,&hour,&min,&sec,&msec);
 sprintf(str,"%04d%02d%02d%02d%02d%02d",year,month,day,hour,min,sec);
 printf("%s ",str);   
 scanf(str);
 return 0;
    

}

 

源代码：
http://download.youkuaiyun.com/detail/xinzheng_wang/3563465