std::chrono::tai_clock - Man Page

using duration
using period
using rep
using time_point

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