implicit conversion between c++11 clocks/time_points

Is it possible to do implicit/explicit conversion between time_point-s of two C++11 clocks?

Motivation: chrono::duration-s provide means of storing time intervals from epoch, conceptually is not equal with a time_pont of custom clock that has an epoch on its own. Having an implicit conversion between clocks eases up the use Howard Hinnant's date library which provides means to manipulate and print out time_points of system clocks.

Example:

#include <date/date.h>
using namespace date;
namespace ch = std::chrono;
// 
#define EPOCH_OFFSET 100
template<class Duration> using PosixTimePoint = 
                   ch::time_point<ch::system_clock, Duration>;
typedef PosixTimePoint<ch::duration<long,std::micro>> PosixTimePointType;

struct SomeClock{
    typedef ch::duration<long,std::micro>   duration;
    typedef ch::time_point<SomeClock>  time_point;

    ...
    static time_point now() noexcept {
        using namespace std::chrono;
        return time_point (
            duration_cast<duration>( 
                system_clock::now().time_since_epoch()) + date::years(EPOCH_OFFSET) );
    }
    static PosixTimePoint<duration> to_posix( const time_point& tp  ){...}

}
auto tp = SomeClock::now(); //<time_point<SomeClock,ch::duration<long,std::micro>>;

Objective: to convert tp so the std::stream conversions of date.h works and prints out the current time, which in my case is: 2017-12-24 17:02:56.000000

// std::cout << tp; compile error
std::cout << SomeClock::to_posix( tp ); // OK

Explicit cast: this could ease up readability, support conversion feature of the language and facilitate access to date.h routines.

long time_value = static_cast<long>( tp );
auto st = static_cast<PosixTimePointType>( tp ); 
std::cout << static_cast<PosixTimePointType>( tp );