#includeIn this example, the QDate object `date` is initialized with the date value of February 29, 2022. However, 2022 is not a leap year, so February 29 does not exist. Therefore, the `isValid()` function returns false and prints "Date is invalid." The QDate class is part of the Qt Core module, and this function is provided through the Qt Core library.int main(int argc, char *argv[]) { QDate date(2022, 2, 29); if(date.isValid()) { printf("Date is valid.\n"); } else { printf("Date is invalid.\n"); } return 0; }