first of all lets say I have 2 rented cars already:
ID,PlateNumber,StartDate,EndDate,TotalPrice (this line doesn’t show in the csv file its just for reference)

output:

,,,, (this line is always empty and idk why)
3,123456Z,Tue May 07 01:00:00 2024,Wed May 08 01:00:00 2024,200.00$
3,789123B,Tue May 07 01:00:00 2024,Wed May 08 01:00:00 2024,100.00$

(the ID is the user who rented the cars)

and now let’s say user 3 doesn’t want the car of plate 123456Z

when I go ahead and delete the car and open the csv file, it all of a sudden looks like this:

output:

,,,Thu Jan 01 02:00:07 1970,
3,789123B,Thu Jan 01 02:00:00 1970, Thu Jan 01 02:00:07 1970,

and this is all the code related to it:

struct UserInformation {
    string ID;
    string firstName;
    string lastName;
    string password;
    string email;
    string phoneNumber;
    string authority;

    void printUserInformation() const {
        cout << "ID: " << ID << endl;
        cout << "First Name: " << firstName << endl;
        cout << "Last Name: " << lastName << endl;
        cout << "Password: " << password << endl;
        cout << "Email: " << email << endl;
        cout << "Phone Number: " << phoneNumber << endl;
        cout << "Authority: " << authority << endl;
    }
};

struct CarsInformation {
    string type;
    string brand;
    string model;
    string year;
    string subType;
    string color;
    string plateNumber;
    string price;
    string availability;

    void printCarsInformation() const {
        cout << "Type: " << type << endl;
        cout << "Brand: " << brand << endl;
        cout << "Model: " << model << endl;
        cout << "Year: " << year << endl;
        cout << "SubType: " << subType << endl;
        cout << "Color: " << color << endl;
        cout << "Plate Number: " << plateNumber << endl;
        cout << "Price per day: " << price << endl;
        cout << "Availability: " << availability << endl;
    }
};

struct RentInformation {
    string ClientID;
    string CarPlateNumber;
    time_t RentStartDate;
    time_t RentEndDate;
    string TotalPriceForTheRent;
};

this one might have something to do with the empty line:

void appendRentInfoToCSV(const RentInformation& rentInfo) {
    ofstream outputFile("C:\Users\User\Desktop\rented_cars.csv",  ios::out | ios::app);
    if (outputFile.is_open()) {
        char startDateStr[50];
        char endDateStr[50];

        strftime(startDateStr, sizeof(startDateStr), "%a %b %d %H:%M:%S %Y", localtime(&rentInfo.RentStartDate));
        strftime(endDateStr, sizeof(endDateStr), "%a %b %d %H:%M:%S %Y", localtime(&rentInfo.RentEndDate));

        outputFile << rentInfo.ClientID << ',' << rentInfo.CarPlateNumber << ','
                   << startDateStr << ',' << endDateStr << ','
                   << fixed << setprecision(2) << rentInfo.TotalPriceForTheRent << endl;
        cout << "Reservation information added successfully." << endl;
        outputFile.close(); // Close the file inside the if block
    } else {
        cerr << "Failed to open file for writing." << endl;
    }
}

this is the function:

void cancelRESERVATION(CarsInformation cars[], int& numCars, RentInformation rents[], int& numRents, UserInformation users[], int& numUsers, string userID) {
    // Open the rented_cars.csv file to read the reservations
    ifstream inputFile("C:\Users\User\Desktop\rented_cars.csv");
    if (!inputFile.is_open()) {
        cerr << "Failed to open file for reading." << endl;
        return;
    }

    // Read and display all reservations of the user
    bool hasReservations = false;
    int j = 1;
    string line;
    while (getline(inputFile, line)) {
        // Split the CSV line into fields
        stringstream ss(line);
        string field;
        string fields[5]; // Assuming 5 fields per line
        int fieldIndex = 0;
        while (getline(ss, field, ',')) {
            fields[fieldIndex++] = field;
        }

        // Check if the line corresponds to the current user's reservation
        if (fieldIndex == 5 && fields[0] == userID) {
            // Print reservation information
            cout << "Car #" << j++ << endl;
            cout << "Plate Number: " << fields[1] << endl;
            cout << "Start Date: " << fields[2] << endl;
            cout << "End Date: " << fields[3] << endl;
            cout << "Total Price: " << fields[4] << endl;

            hasReservations = true;
        }
    }
    inputFile.close();

    // If the user has no reservations, inform them and return
    if (!hasReservations) {
        cout << "You have no reservations to cancel." << endl;
        return;
    }

    // Ask the user to enter the plate number of the car they want to cancel the reservation for
    string plateNumber;
    cout << "Enter the plate number of the car you want to cancel the reservation for: ";
    cin >> plateNumber;

    // Find the reservation with the given plate number and user ID
    int index = -1;
    for (int i = 0; i < numRents; i++) {
        if (rents[i].CarPlateNumber == plateNumber && rents[i].ClientID == userID) {
            index = i;
            break;
        }
    }

    // If the reservation is found, cancel it
    if (index != -1) {
        // Move all reservations after the canceled one one position to the left
        for (int i = index; i < numRents - 1; i++) {
            rents[i] = rents[i + 1];
        }
        numRents--;

        // Update the car's availability to "available" in the cars array
        for (int i = 0; i < numCars; i++) {
            if (cars[i].plateNumber == plateNumber) {
                cars[i].availability = "available";
                break;
            }
        }

        // Rewrite the updated list of cars to the CSV file
        ofstream outputFile("C:\Users\User\Desktop\cars.csv");
        if (outputFile.is_open()) {
            for (int i = 0; i < numCars; i++) {
                outputFile << cars[i].type << ',' << cars[i].brand << ',' << cars[i].model << ',' << cars[i].year << ',' << cars[i].subType << ',' << cars[i].color << ',' << cars[i].plateNumber << ',' << cars[i].price << ',' << cars[i].availability << endl;
            }
            outputFile.close();
            cout << "Car availability updated successfully." << endl;
        } else {
            cerr << "Failed to open file for writing." << endl;
        }

        // Rewrite the updated list of reservations to the CSV file
        ofstream outputFile2("C:\Users\User\Desktop\rented_cars.csv");
        if (outputFile2.is_open()) {
            for (int i = 0; i < numRents; i++) {
                char startDateStr[50];
                char endDateStr[50];

                strftime(startDateStr, sizeof(startDateStr), "%a %b %d %H:%M:%S %Y", localtime(&rents[i].RentStartDate));
                strftime(endDateStr, sizeof(endDateStr), "%a %b %d %H:%M:%S %Y", localtime(&rents[i].RentEndDate));

                outputFile2 << rents[i].ClientID << ',' << rents[i].CarPlateNumber << ','
                            << startDateStr << ',' << endDateStr << ','
                            << fixed << setprecision(2) << rents[i].TotalPriceForTheRent << endl;
            }
            outputFile2.close();
            cout << "Updated reservation information written to the CSV file." << endl;
        } else {
            cerr << "Failed to open file for writing." << endl;
        }

        cout << "Reservation canceled successfully." << endl;
    } else {
        cout << "Reservation not found for the provided plate number." << endl;
    }
}

I do not have anything in mind, I just want it to work