Unix Timestamps: What They Are, Why They Break, and How to Convert Them

Unix timestamps count seconds since January 1, 1970 UTC and underpin virtually all date/time systems, but their simplicity masks critical edge cases. Common pitfalls include confusing seconds with milliseconds (especially in JavaScript), the Year 2038 overflow for 32-bit signed integers, negative timestamps for pre-1970 dates, and the deliberate omission of leap seconds.