/*************************************************
 Program to calculate the day of the year from the date
 * 
 * Enter date (MM/DD/YYYY): 12/30/2006
 * Day of year: 364
 *  
 ************************************************/

#include<stdio.h> // include stdio.h library

int main(void)
{
    int day, mon, year, days_in_feb = 28, 
            doy;    // day of year

    printf("Enter date (MM/DD/YYYY): \n");
    scanf("%d/%d/%d", &mon, &day, &year);

    doy = day;

    // check for leap year
    if( (year % 4 == 0 && year % 100 != 0 ) || (year % 400 == 0) )
    {
        days_in_feb = 29;
    }

    switch(mon)
    {
        case 2:
            doy += 31;
            break;
        case 3:
            doy += 31+days_in_feb;
            break;
        case 4:
            doy += 31+days_in_feb+31;
            break;
        case 5:
            doy += 31+days_in_feb+31+30;
            break;
        case 6:
            doy += 31+days_in_feb+31+30+31;
            break;
        case 7:
            doy += 31+days_in_feb+31+30+31+30;
            break;            
        case 8:
            doy += 31+days_in_feb+31+30+31+30+31;
            break;
        case 9:
            doy += 31+days_in_feb+31+30+31+30+31+31;
            break;
        case 10:
            doy += 31+days_in_feb+31+30+31+30+31+31+30;            
            break;            
        case 11:
            doy += 31+days_in_feb+31+30+31+30+31+31+30+31;            
            break;                        
        case 12:
            doy += 31+days_in_feb+31+30+31+30+31+31+30+31+30;            
            break;                                    
    }

    printf("Day of year: %d", doy);

    return 0; // return 0 to operating system
}