www.pudn.com > 日期、菜单、字符串的C函数.rar > JTOG.C

/*                    *** jtog.c ***                                 */ 
/*                                                                   */ 
/* IBM - PC microsoft "C"                                            */ 
/*                                                                   */ 
/* function to convert a julian date (1 = 1st day AD) into a         */ 
/* gregorian date in the format mm/dd/yy.  Returns a 0 if successful */ 
/* or a -1 if not.                                                   */ 
/*                                                                   */ 
/* WARNING - if outdate is not dimensioned at least 9 characters a   */ 
/*           memory overwrite will occure.                           */ 
/*                                                                   */ 
/* Written by L. Cuthbertson, March 1984                             */ 
/*                                                                   */ 
/*********************************************************************/ 
/*                                                                   */ 
 
#define CENTRY 19 
#define TRUE 1 
#define FALSE 0 
  
int jtog(julian,outdate) 
char outdate[]; 
register long julian; 
{ 
	static int monthd[] = {0,31,59,90,120,151,181,212,243,273,304,334}; 
	int centry,leap,i,iyr,imo,iday; 
	static long cdays = 36524, ydays = 365; 
 
	/* reduce julian from 1st day AD to 1st day of CENTRY */ 
	julian -= CENTRY*cdays + CENTRY/4; 
 
	/* determine year */ 
	iyr = julian/ydays; 
	if ((julian - (iyr*ydays + iyr/4)) < 0) 
		iyr -= 1; 
	if (iyr < 0) 
		return(-1); 
 
	/* determine if this is a leap year or not */ 
	if (iyr%4 == 0 && iyr != 0 || CENTRY%4 == 0) 
		leap = TRUE; 
	else 
		leap = FALSE; 
 
	/* determine month */ 
	julian = julian - (iyr*ydays + iyr/4); 
	if (leap) julian += 1; 
	for (imo=12;imo>0;imo--) { 
		i=0; 
		if ((leap) && (imo > 2)) i = -1; 
		if ((julian - monthd[imo-1] + i) > 0) break; 
	} 
	if (imo == 0) imo = 1; 
 
	/* determine day */ 
	iday = julian - monthd[imo-1] + i; 
	if (iday == 0) { 
		iyr -= 1; 
		if (iyr < 0) return(-1); 
		imo = 12; 
		iday = 31; 
	} 
 
	/* transfer into output string */ 
	if (imo > 9) 
		outdate[0] = '1'; 
	else 
		outdate[0] = '0'; 
	outdate[1] = (char)(imo%10 + '0'); 
	outdate[2] = '/'; 
 
	if (iday > 9) 
		outdate[3] = (char)(iday/10 + '0'); 
	else 
		outdate[3] = '0'; 
	outdate[4] = (char)(iday%10 + '0'); 
	outdate[5] = '/'; 
 
	if (iyr > 9) 
		outdate[6] = (char)(iyr/10 + '0'); 
	else 
		outdate[6] = '0'; 
	outdate[7] = (char)(iyr%10 + '0'); 
	outdate[8] = '\0'; 
 
	/* done */ 
	return(0); 
}