Display Number of Days in a Month Using Switch Statement in C

This program displays the number of days in a given month (1-12) using a switch statement, taking leap years into account for February.

C Program

#include <stdio.h>

int main() {
    int month, year, days;

    printf("Enter month (1-12): ");
    scanf("%d", &month);

    printf("Enter year: ");
    scanf("%d", &year);

    switch (month) {
        case 1: case 3: case 5: case 7:
        case 8: case 10: case 12:
            days = 31;
            break;
        case 4: case 6: case 9: case 11:
            days = 30;
            break;
        case 2:
            if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
                days = 29;
            } else {
                days = 28;
            }
            break;
        default:
            printf("Invalid month.\n");
            return 1;
    }

    printf("Number of days in month %d of year %d: %d\n", month, year, days);

    return 0;
}

Explanation

• Grouping case labels without a break between them (e.g. case 1: case 3: ...) lets several months share the same 31-day result.
• February is handled separately since its day count depends on whether year is a leap year.
• The leap year rule is: divisible by 4 and not divisible by 100, unless it’s also divisible by 400 (so 2000 is a leap year, but 1900 is not).
• The default case catches invalid month numbers outside 1-12.

Sample Output

Enter month (1-12): 2
Enter year: 2024
Number of days in month 2 of year 2024: 29

Enter month (1-12): 2
Enter year: 2023
Number of days in month 2 of year 2023: 28