Compare two duration objects for inequality, even if they have distinct representations and/or periods.
template <class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator!=( const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
be implicitly convertible to
or vice versa. If neither can be implicitly converted to the other,
or they are distinct instantiations of duration but each can implicitly
convert to the other, then the expression is ill formed.