> It's weird to talk about "switching" to atomic time. The biggest reason to describe it as "switching from UTC to TAI" (at least for me) is due to Unix time.

> It's weird to talk about "switching" to atomic time. The biggest reason to describe it as "switching from UTC to TAI" (at least for me) is due to Unix time. Unix time is an elegant concept at first glance, ideally it's a free-running, monotonic counter that abstracts us away from timezone problems, an unambiguous representation of time. You only adjust the timezone settings or the timezone database, the time itself is never adjusted. Unfortunately, using UTC rather than TAI as Unix time's foundation is a fatal mistake. As Unix time cannot represent leap seconds, all the previous advantages break down - we had to freeze or advance the Unix time itself to compensate for that limitation. If there's a TAI-based "new Unix time", the leap second handling can be simplified a lot. The underlying time is always correct regardless of leap seconds. Sure, a missed leap second notification makes all civilian time faster or slower by 1 second, but the situation is the same for UTC if there's no time synchronization.