Why do I need to multiply unix timestamps by 1000 in JavaScript?

I'm sure there's a reason I have to add three zeros to every Unix timestamp in JavaScript in order to get the correct date. Can yo开发者_开发问答u tell me why? Is it as simple as milliseconds since the epoch vs. seconds?

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Because Javascript uses milliseconds internally, while normal UNIX timestamps are usually in seconds.

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Javascript uses the number of milliseconds since epoch. Unix timestamp is seconds since epoch.

Hence, the need to convert Unix timestamp into millseconds before using it in Javascript

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Unix time is the number of seconds since the epoch (1 Jan 1970). In Javascript, the Date object expects the number of milliseconds since the epoch, hence the 1000-fold difference.