This proposal was originally written in 2018 as a concrete proposal for numeric time zone identifiers. I'm still not sure if this has a merit or not, but for the historical perspective, I reproduce the (incomplete) proposal in verbatim here. --Kang Seonghoon
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The needs for the short and stable identifier are most importantly observed by the case of the Unicode CLDR project. CLDR required a stable identifier for the locales, which requires a stable identifier for the time zones. [...]