Check expiry date using c language, you should know

It is good habits to check the expiry date of any products like cosmetic products, milk products, etc. Such products can no longer meet safety requirements as soon as the expiry date has been passed.

Sometimes in C application, we need to implement the logic to validate the expiry date of the product. So In this article, I am explaining how you can implement the logic to validate the expiry date of the product to enter their expiry date.

The below program asks the expiry date in the format of years, months, and days. When the user enters the date in the format of years, months and days then it validates the expiry date on the basis of the current date.

Some products have a barcode for the expiry date in that situation there should be a barcode scanner that reads the expiry date from the products and send the expiry date to the application to validate the expiry date. So let see a simple logic to verify the expiry date of the product.

I am following the below steps to accomplish the program,

Enters years, months, and days.
Verify the validity of the expiry date.
Get current time from the system.
Now check the expiry date.

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See below program to check the expiry date,

#include <stdio.h>
#include <time.h>

#define MAX_YR  9999
#define MIN_YR  1900


//structure to store date
typedef struct
{
    int yyyy;
    int mm;
    int dd;
} Date;


// Function to check leap year.
//Function returns 1 if leap year
int  IsLeapYear(int year)
{
    return (((year % 4 == 0) &&
             (year % 100 != 0)) ||
            (year % 400 == 0));
}

// returns 1 if given date is valid.
int isValidDate(Date *validDate)
{
    //check range of year,month and day
    if (validDate->yyyy > MAX_YR ||
            validDate->yyyy < MIN_YR)
        return 0;
    if (validDate->mm < 1 || validDate->mm > 12)
        return 0;
    if (validDate->dd < 1 || validDate->dd > 31)
        return 0;

    //Handle feb days in leap year
    if (validDate->mm == 2)
    {
        if (IsLeapYear(validDate->yyyy))
            return (validDate->dd <= 29);
        else
            return (validDate->dd <= 28);
    }

//handle months which has only 30 days
    if (validDate->mm == 4 || validDate->mm == 6 ||
            validDate->mm == 9 || validDate->mm == 11)
        return (validDate->dd <= 30);

    return 1;
}

//return 1 if successfully enter the expiry date
int enterExpiryDate(Date *getDate)
{
    printf("\n Enter year = ");
    scanf("%d",&getDate->yyyy);
    printf("\n\n Enter month = ");
    scanf("%d",&getDate->mm);
    printf("\n\n Enter day = ");
    scanf("%d",&getDate->dd);
    return isValidDate(getDate);
}


//function to validate product expiry date
int checkExpiryDate(const Date* expiryDate, const Date * currentDate)
{
    if (NULL==expiryDate||NULL==currentDate)
    {
        return 0;
    }
    else
    {
        if (expiryDate->yyyy > currentDate->yyyy)
        {
            return 0;
        }
        else if (expiryDate->yyyy < currentDate->yyyy)
        {
            return 1;
        }
        else
        {
            if (expiryDate->mm > currentDate->mm)
            {
                return 0;
            }
            else if (expiryDate->mm < currentDate->mm)
            {
                return 1;
            }
            else
            {
                return (expiryDate->dd >= currentDate->dd)? 0 : 1;
            }
        }
    }
}

int main(void)
{
    time_t rawtime;
    struct tm * timeinfo;

    //variable to store expiry date
    Date expiryDate = {0};

    //variable to store expiry date
    Date currentDate = {0};
    int status = 0;
    int button = 0;

    printf("\n\n Please enter product expiry date!\n");
    status = enterExpiryDate(&expiryDate);
    if(status !=1)
    {
        printf("\n\n Please enter a valid date!\n");
        return 0;
    }

    //Get current time
    time(&rawtime);
    timeinfo = localtime(&rawtime);

    //compose current date

    // years since 1900
    currentDate.yyyy = timeinfo->tm_year+1900;

    // months since January - [0, 11]
    currentDate.mm = timeinfo->tm_mon+1;

    // day of the month - [1,28 or 29 or 30 or 31]
    currentDate.dd = timeinfo->tm_mday;

    printf("\n\n Enter 5 to check product expiry date  = ");
    scanf("%d",&button);

    if((button != 5))
    {
        printf("\n\n You have prssed invalid button !!!\n\n");

        return 0;
    }

    //check expiry date
    status = checkExpiryDate(&expiryDate,&currentDate);
    if(status !=0)
    {
        printf("\n\n Product date has been expired !!!\n");
    }
    else
    {
        printf("\n\n You can use !!!\n");
    }

    return 0;
}

Output:

Current date: 7/9/2018

Code Analysis:

In the above c code example, first, we ask the users to enter the expiry date of the product. Using the if condition I am verifying the validity of the entered date.

status = enterExpiryDate(&expiryDate);
if(status !=1)
{
    printf("\n\n Please enter a valid date!\n");
    return 0;
}

Now get the time using the time function. This function returns the time since 00:00:00 UTC, January 1, 1970 (Unix timestamp) in seconds. So we have to calculate the current time.

//Get current time
time(&rawtime);
timeinfo = localtime(&rawtime);

//compose current date

// years since 1900
currentDate.yyyy = timeinfo->tm_year+1900;

// months since January - [0, 11]
currentDate.mm = timeinfo->tm_mon+1;

// day of the month - [1,28 or 29 or 30 or 31]
currentDate.dd = timeinfo->tm_mday;

Now expiry date checker C program asks the user to hit 5 from the keyboard to validate the expiry date of the product. If the user enters 5, the code checks the expiry date and displays the result on the console.

printf("\n\n Enter 5 to check product expiry date  = ");
scanf("%d",&button);

if((button != 5))
{
    printf("\n\n You have prssed invalid button !!!\n\n");

    return 0;
}

//check expiry date
status = checkExpiryDate(&expiryDate,&currentDate);
if(status !=0)
{
    printf("\n\n Product date has been expired !!!\n");
}
else
{
    printf("\n\n You can use !!!\n");
}