Date and time can be complicated due to different perspectives of local time versus coordinated universal time and assumptions that do not always hold true. Time zones are political and subject to change, and date and time calculations involve subtleties around daylight saving time transitions, leap years, and distinguishing between date math and time math. To properly work with dates and times, it is important to consider all perspectives, make no assumptions, use a quality library like Moment.js that handles time zone and parsing complexities, and remember that time zones are not fixed and can change rapidly.