template <class Clock, class Duration1, class Duration2>
bool operator==(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_since_epoch() == rhs.time_since_epoch().
template <class Clock, class Duration1, class Duration2>
bool operator!=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(lhs == rhs).
template <class Clock, class Duration1, class Duration2>
bool operator<(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_since_epoch() < rhs.time_since_epoch().
template <class Clock, class Duration1, class Duration2>
bool operator<=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(rhs < lhs).
template <class Clock, class Duration1, class Duration2>
bool operator>(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: rhs < lhs.
template <class Clock, class Duration1, class Duration2>
bool operator>=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(lhs < rhs).