std::chrono::tai_clock - Man Page

using duration = chrono::duration< rep, period >
using period = system_clock::period
using rep = system_clock::rep
using time_point = chrono::time_point< tai_clock >

template<typename _Duration > static tai_time< common_type_t< _Duration, seconds > > from_utc (const utc_time< _Duration > &__t)
static time_point now ()
template<typename _Duration > static utc_time< common_type_t< _Duration, seconds > > to_utc (const tai_time< _Duration > &__t)

static constexpr bool is_steady