Time Until Date Calculator

The target date and time inputs are validated and then converted to a UTC timestamp using the browser's local timezone. The current moment is obtained from the browser clock and compared against the target timestamp. The absolute difference in milliseconds is then broken into components: total days are derived by dividing total milliseconds by 86,400,000 and flooring the result; remaining hours are extracted by dividing the leftover milliseconds by 3,600,000 and flooring; and remaining minutes are calculated from what is left after accounting for days and hours. If the target moment is in the past, the calculator automatically detects this because the difference is negative, and it displays elapsed time since the target instead of time remaining, switching the label to 'Time Since Target' to avoid confusion.