把日期和时间转换成DOS格式

[c]代码库

#include <stdio.h> 
#include <dos.h> 

char *month[] = {"---", "Jan", "Feb", "Mar", "Apr", "May", "Jun", 
                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; 

#define SECONDS_PER_DAY 86400L  /* the number of seconds in one day */ 

struct date dt; 
struct time tm; 

int main(void) 
{ 
   unsigned long val; 

/* get today's date and time */ 
   getdate(&dt); 
   gettime(&tm); 
   printf("today is %d %s %d\n", dt.da_day, month[dt.da_mon], dt.da_year); 

/* convert date and time to unix format (number of seconds since Jan 1, 1970 */ 
   val = dostounix(&dt, &tm); 
/* subtract 42 days worth of seconds */ 
   val -= (SECONDS_PER_DAY * 42); 

/* convert back to dos time and date */ 
   unixtodos(val, &dt, &tm); 
   printf("42 days ago it was %d %s %d\n", 
        dt.da_day, month[dt.da_mon], dt.da_year); 
   return 0; 
}