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

/*                     *** weekday.c ***                             */ 
/*                                                                   */ 
/* IBM - PC microsoft "C"                                            */ 
/*                                                                   */ 
/* function to determine the day of the week a given gregorian date  */ 
/* falls on.  Returns a 0 if successful or a -1 if not.              */ 
/*                                                                   */ 
/* WARNING - day must be declared to be at least 10 characters or a  */ 
/*           memory overwrite will occure.                           */ 
/*                                                                   */ 
/* Written by L. Cuthbertson, March 1983                             */ 
/*                                                                   */ 
/*********************************************************************/ 
/*                                                                   */ 
 
int weekday(indate,day) 
char indate[],day[]; 
{ 
	static char days [7][10] = {'S','u','n','d','a','y','\0',' ',' ',' ', 
	                            'M','o','n','d','a','y','\0',' ',' ',' ', 
	                            'T','u','e','s','d','a','y','\0',' ',' ', 
	                            'W','e','d','n','e','s','d','a','y','\0', 
	                            'T','h','u','r','s','d','a','y','\0',' ', 
	                            'F','r','i','d','a','y','\0',' ',' ',' ', 
	                            'S','a','t','u','r','d','a','y','\0',' '}; 
	int iday; 
	long julian,gtoj(); 
 
	/* get julian date */ 
	if ((julian = gtoj(indate)) == (-1)) return(-1); 
 
	/* calculate day of week */ 
	iday = (julian-1) % 7; 
 
	/* move weekday into character string */ 
	strcpy(day,days[iday]); 
 
	/* done */ 
	return(0); 
}