The mini-project “Calendar in C” is a console application using the C programming language. This project compiles in Code Blocks with the GCC compiler. In this console application, you can check the date for the given month and year.
In this project, we are using Zeller’s Congruence. Zeller’s congruence is an algorithm devised by Christian Zeller in the 19th century to calculate the day of the week for any Julian or Gregorian calendar date. It can be considered to be based on the conversion between Julian day and the calendar date.
Check the below C code for the calendar. The below code allows you to navigate year or month using the arrow key of your keyboard. Later I will update the explanation of the code.
#include<stdio.h>
//check leap year
#define IS_LEAP_YEAR(Year) ((Year%4==0 && Year%100 != 0)||Year%400==0)
/*Function returns the index of the days
of the given month and year using ZELLER'S ALGORITHM
For e.g-
Index Day
0 Sunday
1 Monday
2 Tuesday
3 Wednesday
4 Thursday
5 Friday
6 Saturday*/
int getZeller(int Month,int Year)
{
int Day = 1, ZMonth, ZYear, Zeller;
if(Month < 3)
ZMonth = Month+10;
else
ZMonth = Month-2;
if(ZMonth > 10)
ZYear = Year-1;
else
ZYear = Year;
Zeller = ((int)((13*ZMonth-1)/5)+Day+ZYear%100+
(int)((ZYear%100)/4)-2*(int)(ZYear/100)+
(int)(ZYear/400)+77)%7;
return Zeller;
}
/* A Function to return the number of days in
a month
Month Number Name Number of Days
0 January 31
1 February 28 (non-leap) / 29 (leap)
2 March 31
3 April 30
4 May 31
5 June 30
6 July 31
7 August 31
8 September 30
9 October 31
10 November 30
11 December 31
*/
int getNumberOfDays(int monthNumber, int year)
{
int MonthDay[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
MonthDay[monthNumber-1] += (IS_LEAP_YEAR(year) && (monthNumber == 2));
return (MonthDay[monthNumber-1]);
}
//Align the message
void printMessageCenter(const char* message)
{
int len =0;
int pos = 0;
//calculate how many space need to print
len = (78 - strlen(message))/2;
printf("\t\t\t");
for(pos =0 ; pos < len ; pos++)
{
//print space
printf(" ");
}
//print message
printf("%s",message);
}
// Function to print the calendar of the given year
void printCalendar(int month,int year)
{
//get month name
char * months[] = {"January", "February", "March",
"April", "May", "June",
"July", "August", "September",
"October", "November", "December"
};
char buf[32] = {0};
int j,k;
sprintf(buf,"%s%d\n\n","Calendar - ",year);
printMessageCenter(buf);
int days;
// Index of the day from 0 to 6
int current = getZeller(month,year);
days = getNumberOfDays (month, year);
// Print the current month name
printMessageCenter(months[month-1]);
printf("\n");
// Print days in the columns
printf(" Sun Mon Tue Wed Thu Fri Sat\n");
// Print appropriate spaces
for (k = 0; k < current; k++)
printf(" ");
//print days as per the month
for (j= 1; j <= days; j++)
{
printf("%5d", j);
++k; //change new line for each week
if (k > 6)
{
k = 0;
printf("\n");
}
}
if (k)
printf("\n");
current = k;
}
void headMessage(const char *message)
{
system("cls");
printf("\t\t\t###########################################################################");
printf("\n\t\t\t############ ############");
printf("\n\t\t\t############ C Project: Calendar For Given Month. ############");
printf("\n\t\t\t############ ############");
printf("\n\t\t\t###########################################################################");
printf("\n\t\t\t---------------------------------------------------------------------------\n");
printMessageCenter(message);
printf("\n\t\t\t----------------------------------------------------------------------------");
}
void welcomeMessage()
{
headMessage("www.aticleworld.com");
printf("\n\n\n\n\n");
printf("\n\t\t\t **-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**\n");
printf("\n\t\t\t =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
printf("\n\t\t\t = Program =");
printf("\n\t\t\t = Shows =");
printf("\n\t\t\t = calendar of a =");
printf("\n\t\t\t = Given Month =");
printf("\n\t\t\t = =");
printf("\n\t\t\t =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
printf("\n\t\t\t **-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**-**\n");
printf("\n\n\n\t\t\t Enter any key to continue.....");
getchar();
system("cls");
printf("\n\tThis program shows calendar of a given month.\n\n");
}
int main()
{
int Month, Year;
welcomeMessage();
//validate input
while(1)
{
fflush(stdin);
printf("Enter the Year YYYY = ");
scanf("%d",&Year);
printf("Enter the Month = ");
scanf("%d", &Month);
if(Year < 0)
{
printf("\nInvalid year value...");
continue;
}
if(Year < 100)
Year += 1900;
if(Year < 1582 || Year > 4902)
{
printf("\nInvalid year value...");
continue;
}
if(Month < 1 || Month > 12)
{
printf("\nInvalid month value...");
continue;
}
break;
} /*Break loop after valid input*/
//clean console
system("cls");
do
{
printCalendar(Month,Year);
//Display message
printf("\n\n\t\t(*) Press Up Arrow for Next Year.");
printf("\n\n\t\t(*) Press Down Arrow for Previous Year.");
printf("\n\n\t\t(*) Press Right Arrow for Next Month.");
printf("\n\n\t\t(*) Press Left Arrow for Previous Month.");
printf("\n\n\t\t(*) Press ESC for Exit.\n\n\n\t\t");
char KeyCode = getch(); /* getting Key Code */
if(KeyCode == 72) /* Up Arrow */
Year++;
if(KeyCode == 80) /* Down Arrow */
Year--;
if(KeyCode == 77) /* Right Arrow */
{
Month++;
if(Month > 12)
{
Month = 1;
Year++;
}
}
if(KeyCode == 75) /* Left Arrow */
{
Month--;
if(Month < 1)
{
Month = 12;
Year--;
}
}
if(KeyCode == 27) /* Esc button */
{
system("cls");
printf("\n\n\n\n\n\t\tBye Bye ...");
printf("\n\t\tThanks for reading Aticleworld\n\n\n\n\n\n");
exit(1);
}
system("cls");
}
while(1);
return (0);
}
Output:
Screen 1:
This is the first welcome screen that asks you to press any key on your keyboard.
Screen 2:
After pressing the key on your keyboard a second screen will prompt. The second screen will ask you to enter the valid year and month.
Screen 3:
This screen will show the date and day according to your input. This screen also allows you to see the day and date of the next and previous year and month; you just need to press the arrow button as per the description.
For example, if you want to see the calendar for the next year you just need to press the “up arrow (↑)” button.
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