(1) template< class Clock, class Dur1, class Dur2 >
bool operator==( const time_point<Clock,Dur1>& lhs,
const time_point<Clock,Dur2>& rhs ); (since C++11) (until C++14) template< class Clock, class Dur1, class Dur2 >
constexpr bool operator==( const time_point<Clock,Dur1>& lhs,
const time_point<Clock,Dur2>& rhs ); (since C++14) (2) template< class Clock, class Dur1, class Dur2 >