Introduction -- Header -- Construction -- Construct from String -- Construct from Clock -- Construct using Conversion functions -- Accessors -- Conversion To String -- Operators

Introduction

The class boost::posix_time::ptime is the primary interface for time point manipulation. In general, the ptime class is immutable once constructed although it does allow assignment.

Class ptime is dependent on gregorian::date for the interface to the date portion of a time point.

Other techniques for creating times include time iterators.

Header

      #include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o
      or
      #include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types
    

Construction

Construct from String

Construct from Clock

Construct using Conversion Functions

Accessors

Conversion to String

Operators

top

Introduction -- Header -- Construction -- Count Based Construction -- Construct from String -- Accessors -- Conversion To String -- Operators

Introduction

The class boost::posix_time::time_duration the base type responsible for representing a length of time. A duration can be either positive or negative. The general time_duration class provides a constructor that takes a count of the number of hours, minutes, seconds, and fractional seconds count as shown in the code fragment below. The resolution of the time_duration is configureable at compile time. See Build-Compiler Information for more information.

      using namespace boost::posix_time;
      time_duration td(1,2,3,4); //01:02:03.000000004 when resolution is nano seconds
      time_duration td(1,2,3,4); //01:02:03.000004 when resolution is micro seconds
    

Several small helper classes that derive from a base time_duration, as shown below, to adjust for different resolutions. These classes can shorten code and make the intent clearer.

As an example:

  
      using namespace boost::posix_time;
      
      time_duration td = hours(1) + seconds(10); //01:00:01
      td = hours(1) + nanosec(5); //01:00:00.000000005
    

Note that the existence of the higher resolution classes (eg: nanosec) depends on the installation of the library. See Build-Compiler Information for more information.

Header

      #include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o
      or
      #include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types
    

Construction

Count Based Construction

Construct from String

Accessors

Conversion To String

Operators

top

Introduction -- Header -- Construction -- Accessors -- Conversion To String -- Operators

Introduction

The class boost::posix_time::time_period provides direct representation for ranges between two times. Periods provide the ability to simplify some types of calculations by simplifying the conditional logic of the program.

The time periods example provides an example of using time periods.

Header

      #include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o
      or
      #include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types
    

Construction

Accessors

Conversion To String

Operators

top

Introduction -- Header -- Overview -- Operators

Introduction

Time iterators provide a mechanism for iteration through times. Time iterators are similar to Bidirectional Iterators. However, time_iterators are different than standard iterators in that there is no underlying sequence, just a calculation function. In addition, time_iterators are directly comparable against instances of class ptime. Thus a second iterator for the end point of the iteration is not required, but rather a point in time can be used directly. For example, the following code iterates using a 15 minute iteration interval. The print hours example also illustrates the use of the time_iterator.

      
	#include "boost/date_time/posix_time/posix_time.hpp"
	#include <iostream>


	int
	main()
	{
	  using namespace boost::gregorian;
	  using namespace boost::posix_time;
	  date d(2000,Jan,20);
	  ptime start(d);
	  ptime end = start + hours(1);
	  time_iterator titr(start,minutes(15)); //increment by 15 minutes
	  //produces 00:00:00, 00:15:00, 00:30:00, 00:45:00
	  while (titr < end) {
	    std::cout << to_simple_string(*titr) << std::endl;
	    ++titr;
	  }
	  std::cout << "Now backward" << std::endl;
	  //produces 01:00:00, 00:45:00, 00:30:00, 00:15:00
	  while (titr > start) {
	    std::cout << to_simple_string(*titr) << std::endl;
	    --titr;
	  }
	}
      
    

Header

      #include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o
      or
      #include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types
    

Overview

Operators

top

Introduction -- Header -- Overview

Introduction

A frequent problem in time representation is the conversion between various local time systems. In general this is accomplished by using a reference time system. The reference time system is typically UTC.

Since the posix_time system does no internal time adjustment it can be used to represent both local times and UTC times. However, the user is currently left to handle conversions and time zone knowledge explicitly.

The library offers two different ways to perform UTC to local conversions. The first is using the time zone settings of the computer. This is a useful solution for converting a UTC time for a user machine. This approach depends on the ctime API and will provide incorrect results if the environment is set incorrectly. The other approach allows conversion from any zone to UTC and back independent of the settings of the time zone settings of the computer. The local utc conversion example demonstrates both of these techniques.

Header

      #include "boost/date_time/gregorian/gregorian.hpp" //include all types plus i/o
      or
      #include "boost/date_time/gregorian/gregorian_types.hpp" //no i/o just types
    

Overview

top