C Program to find day of week given date

Question

Is there a way to find out day of the week given date in just one line of C code?

For example

Given 19-05-2011(dd-mm-yyyy) gives me Thursday

Answer 1

/*
Program to calculate the day on a given date by User
*/

#include
#include
#include
void main()
{
int dd=0,mm=0,i=0,yy=0,odd1=0,todd=0;//variable declaration for inputing the date
int remyr=0,remyr1=0,lyrs=0,oyrs=0,cyr=0,upyr=0,leap=0;//variable declaration for calculation of odd days
int montharr[12]={31,28,31,30,31,30,31,31,30,31,30,31};//array of month days
clrscr();
printf("Enter the date as DD-MM-YY for which you want to know the day\t:");
scanf("%d%d%d",&dd,&mm,&yy);  //input the date
/*
check out correct date or not?
*/
if(yy%100==0)
    {
    if(yy%400==0)
        {
        //its the leap year
        leap=1;
        if(dd>29&&mm==2)
            {

            printf("You have entered wrong date");
            getch();
            exit(0);
            }
        }
    else if(dd>28&&mm==2)
        {
        //not the leap year
        printf("You have entered wrong date");
        getch();
        exit(0);

        }
    }
else if(yy%4==0)
    {
    //again leap year
    leap=1;
    if(dd>29&mm==2)
        {
        printf("You have entered wrong date");
        getch();
        exit(0);

        }
    }
else if(dd>28&&mm==2)
    {
    //not the leap year
    printf("You have entered wrong date");
    getch();
    exit(0);

    }
//if the leap year feb month contains 29 days
if(leap==1)
{
montharr[1]=29;

}
//check date,month,year should not be beyond the limits

if((mm>12)||(dd>31)|| (yy>5000))
    {
    printf("Your date is wrong");
    getch();
    exit(0);

    }
//odd months should not contain more than 31 days
if((dd>31 && (mm == 1||mm==3||mm==5||mm==7||mm==8||mm==10||mm==12)))
    {
    printf("Your date is wrong");
    getch();
    exit(0);

    }
//even months should not contains more than 30 days

if((dd>30 && (mm == 4||mm==6||mm==9||mm==11)))
    {
    printf("Your date is wrong");
    getch();
    exit(0);

    }

//logic to calculate odd days.....
printf("\nYou have entered date: %d-%d-%d ",dd,mm,yy);
remyr1=yy-1;
remyr=remyr1%400;

cyr=remyr/100;
if(remyr==0)
    {
    oyrs=0;
    }
else if(cyr==0 && remyr>0)
    {
    oyrs=0;
    }


else if(cyr==1)
    {
    oyrs=5;
    }
else if(cyr==2)
    {
    oyrs=3;
    }
else if(cyr==3)
    {
    oyrs=1;
    }

    upyr=remyr%100;
    lyrs=upyr/4;
    odd1=lyrs+upyr;
    odd1=odd1%7;
    odd1=odd1+oyrs;
    for(i=0;i7)
        todd=todd%7;    //total odd days gives the re quired day....
    printf("\n\nThe day on %d-%d-%d :",dd,mm,yy);

    if(todd==0)
        printf("Sunday");
    if(todd==1)
        printf("Monday");
    if(todd==2)
        printf("Tuesday");
    if(todd==3)
        printf("Wednesday");
    if(todd==4)
        printf("Thrusday");
    if(todd==5)
        printf("Friday");
    if(todd==6)
        printf("Saturday");
getch();
}