A practical guide for fullstack developers to handle dates, times, and timezones in distributed systems: outlines pitfalls (timezone conversions, clock skew, DST), advocates a single timezone (UTC), storing timestamps in UTC, ISO 8601 with zone info, and synchronized clocks; recommends NTP, Java 8/Joda-Time, Moment.js/Luxon, and epoch timestamps; illustrated by e-commerce, IoT, and global event scheduling to ensure accuracy and scalability.