Unix timestamps are everywhere. APIs, databases, logs, JavaScript and authentication tokens all use them, and they cause a surprising number of bugs. Is 1790186400 a date? What about 1790186400000 ? Does a Unix timestamp contain a time zone? Why does JavaScript sometimes show a date in your local time when the timestamp itself is supposed to be UTC? This article explains how Unix timestamps actually work, the difference between seconds and milliseconds, how time zones fit into the pictu...