date-calc.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


void getNextDay(char* input, char* output, int buffersize);
int a2i(const char *s);

/*

	Demo c-code to calculate the next date.
	2015 - F.Bentele

*/
int main(int argc, char const *argv[])
{
	char input[11], output[11];
	printf("Enter the date: ");
	fgets(input, 100, stdin);

	printf("The next day after %s is being calculated...\n", input);
	
	getNextDay(input, output, 11);

	printf("\nAnd the result is: %s\n", output);

	return 0;
}

void getNextDay(char* input, char* output, int buffersize)
{
	int i = 0;
	int day = 0;
	int month = 0;
	int year = 0;

	char* token = strtok(input,".");
	if(token)
	{
		day = atoi(token);
		printf("Day as int: %d\n", day);
		i++;

		while ((token = strtok(NULL, ".")))
		{
			if(i==1)
			{
				month = atoi(token);
				printf("Month: %d\n", month);
			}

			if(i==2)
			{
				year = atoi(token);
				printf("Year: %d\n", year);
			}

			i++;
		}
	}

	switch(day)
	{
		case 31: 
			switch(month)
			{
				case 12: 
					day = 1;
					month = 1;
					year++;
					break;
				default:
					day = 1;
					month++;
					break;
			}
			break;
		case 30:
			switch(month)
			{
				case 4:
				case 6:
				case 9:
				case 11:
					day = 1;
					month++;
					break;
				default:
					day++;
					break;
			}
			break;
		case 29:
			if(month == 2 && year%4 == 0)
			{
				day=1;
				month++;
			} else {
				day++;
			}
			break;
		case 28:
			if(month == 2){
				day=1;
				month++;
			}
			break;
		default:
			day++;
			break;
	}
	
	char* string;
	sprintf(string, "%d.%d.%d\n", day, month, year);
	strncpy(output, string, buffersize-1);
}