> I'm particularly interested in efficient binary serialization of date_time types and/or conversion to integer(s).
 
 
I also can't see any access to the internal value, so what you can do instead is to make some time_duration, and use it instead of the absolute ptime. Like this:
 
 pt::ptime epoch(greg::date(1970, 1, 1));  // or some other reference point
 pt::time_duration duration = t - epoch;
 boost::int64_t diff = duration.total_seconds(); // or total_microseconds() or ticks()
Similarly, you can reconstruct the ptime later.