DateTime: high resolution treatment of time with Julia



For some reasons I fail to use Datetime correctly, can someone point out what I am doing wrong?

C++11 clock provides a time_point, representation (short,long, float, … ) with duration from a given epoch with some properties such es leap seconds,years etc…
I am looking for similar treatment, and wondering if it is possible to have now{Nanoseconds}( ) returning a high resolution event from a given Epoch?

# using POSIX TIME
T = unix2datetime(0) + Microsecond(123456)
Base.Dates.UTInstant{Base.Dates.Millisecond}(62135683200000 milliseconds)

#  using native call:  now() 
T = now() + Nanoseconds(123456)
Base.Dates.UTInstant{Base.Dates.Millisecond}(63655165713147 milliseconds)

Where did my Microseconds go?