Re: [boost] date_time -> ptime

From: Philip Miller (pwmiller_at_[hidden])
Date: 2003-09-03 16:09:08

David Abrahams wrote:

> I'm trying to get a ptime relative to 1/1/1970, so I did:
>
>     using namespace boost::date_time;
>     ptime d;
>     ...
>     boost::posix_time::time_duration since_1970 = d - 1/Jan/1970;
>
> Error.
>
> Since it is a completely lossless conversion (like an upcast), I'd
> like to see boost::date -> boost::posix_time::ptime implicit
> conversions added.

Can you elaborate on the problem?  I, too, am doing lots of conversions between
the boost::date_time library date, ptime, and duration instances with the
conventional unix/posix dawn of time, 1/1/1970.  To my knowledge (perhaps in
ignorance), I have had no problems using constructs similar to

ptime time0( date(1970, 1, 1 ) );
ptime t1;
...
time_duration dt = t1 - time0;

Is the problem that you want to do this with date instances and not time
instances?

With regards to another posting you made, I also work to work with in sub-second
time precision and have had a problem understanding the nuances of clock
ticks/resolutions.  As a simple user I have not had many (if any) problems getting
the library to do what I want, given that my assumption that
time_duration::fractional_seconds returns microseconds is correct.  If/when this
assumption becomes invalid (i.e., date_time changes its internal representation
for msvc or I work on a platform that uses nanoseconds for fractional_seconds),
then I will be in trouble and have to fix a few places spots in my code.  So, I
would like to see a standard time_duration accessor that returns microseconds
rather than the compile-time dependent fractional_seconds.

Phil