Countdown TimerCreate a live countdown to any future date and time with days, hours, minutes, and seconds.

The countdown uses React's useState and useEffect hooks with a setInterval that fires every 1000ms. On each tick, it computes the difference between the target timestamp and Date.now(), then divides the remaining milliseconds into days, hours, minutes, and seconds using integer division and modulo operations. When the difference becomes negative (event has passed), the timer displays zeros and a "past event" message. The cleanup function in useEffect's return clears the interval to prevent memory leaks when the component unmounts. The target date is constructed by concatenating the date and time inputs into a parseable string format (YYYY-MM-DDThh:mm:00). Numbers are padded with leading zeros using String.padStart(2, "0") for consistent visual formatting.