[Boost-users] Re: Date Time lib and time_t

From: Matt Schuckmann (matthew_schuckmann_at_[hidden])
Date: 2004-07-28 12:50:04

You are right it does work however I've got another problem.

The standard ::ctime function takes a time_t adjusts for the local time zone
and converts it to printable string,
There doesn't appear to be an equivalent for the ptime, ie I haven't been
able to figure out how to create a ptime object from a time_t, adjust it for
the local time zone and generate a printable string that shows the correct
time for this the local time zone. It's almost like you need another
parameter for from_time_t() or  to_??_string() to indicated if it's local
time or UTC time or ?
That or some other flag or operation to indicate that a ptime is in UTC time
and you want to convert it into local time.

Am I making sense here? Does this seem reasonable?

I was also wondering if you plan to impliment any more options for
converting to and from strings to ptime's.
You've implimented a rather limited set.

It would be especially nice if you implimented a format type function that
works like strftime().

Matt S.

"Jeff Garland" <jeff_at_[hidden]> wrote in message
news:20040723002145.M7047_at_crystalclearsoftware.com...
> On Thu, 22 Jul 2004 07:45:15 -0700, Matt Schuckmann wrote
> > Has anybody ever implimented a to_time_t function/method for the
> > ptime class to create a time_t from a ptime. I tried doing it
> > similar to the way from_time_t does it but I'm not getting the right
> > answer.
> >
> > It's nice that you can convert from a time_t for use with legacy
> > code but sometimes you need to go back the other way.
> >
> > Herer is my to_time_t function that does not appear to be working
> > inline
> > std::time_t to_time_t(ptime t)
> > {
> >    if( t == neg_infin )
> >       return 0;
> >    else if( t == pos_infin )
> >       return LONG_MAX;
> >    ptime start(gregorian::date(1970,1,1),time_duration(0,0,0));
> >    return (t-start).total_seconds();
> > }
>
> Odd. It works fine for me.  Here's my slightly cleaned up version with
command
> line interface for testing:
>
> #include "boost/date_time/posix_time/posix_time.hpp"
> #include <string>
> #include <iostream>
>
> using namespace boost::posix_time;
> using namespace boost::gregorian;
>
> inline
> std::time_t to_time_t(ptime t)
> {
>   if( t == neg_infin )
>      return 0;
>   else if( t == pos_infin )
>      return LONG_MAX;
>   ptime start(date(1970,1,1));
>   return (t-start).total_seconds();
> }
>
>
> int
> main()
> {
>   std::cout << "***** Time_t calculator *****" << std::endl;
>   std::cout << "Enter a time as in yyyy-mm-dd hh:mm:ss format" <<
std::endl;
>   std::cout << "For example: 2003-3-25 00:55:26" << std::endl;
>   std::cout << "Time: ";
>   std::string ts;
>   std::getline(std::cin, ts);
>   ptime t2 = time_from_string(ts);
>   std::cout << "seconds since 1/1/1970: " << to_time_t(t2) << std::endl;
> }
>
> Couple of runs:
>
> ***** Time_t calculator *****
> Enter a time as in yyyy-mm-dd hh:mm:ss format
> For example: 2003-3-25 00:55:26
> Time: 2003-3-25 00:56:26
> seconds since 1/1/1970: 1048553786
>
> ***** Time_t calculator *****
> Enter a time as in yyyy-mm-dd hh:mm:ss format
> For example: 2003-3-25 00:55:26
> Time: 1970-1-1 0:0:1
> seconds since 1/1/1970: 1
>
> What is your environment (compiler, boost version, etc)?
>
> Jeff