Epoch time + msecs

[Handyman via Digitalmars-d-learn]

How to get current time as a float (or a double or a real) as a 
Unix epoch + milliseconds (e.g, 1447437383.465, or even 
1447437383.46512 with finer resolution)?   I read 
http://dlang.org/intro-to-datetime.html and the docs of course.  
I came this far

    auto ct = Clock.currTime();
    auto milliseconds = ct.fracSec.msecs;
    auto epoch = ct.toUnixTime();

But I think this is not the shortest way and I don't know how to 
combine and cast into a float (or a double or a real).

My goal was to multiply by 1000 and feed as this number as a seed 
to D's random number generator.  But there may be beter ways to 
make a seed.