Maybe a little tricky to get at std::chrono without CCTZ and Rcpp but doable. Would forgo the formatting, parsing, TZ help.
At a strict minimum someone driven-enough could extend Simon's fasttime to return two doubles (in UTC time) as we do -- which would cover parsing. Formating could be done as a kludge with strftime and sprintf as we already do for fractional seconds. Likely brittle though.
Maybe someone should just port CCTZ to Windows? Or maybe just build it and have it skip TZ operations for lack of zoneinfo and still parse / format at UTC?
We solved this, no?
Yes, pending release.