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[wxWidgets.git] / include / wx / datetime.h

/////////////////////////////////////////////////////////////////////////////
// Name:        wx/datetime.h
// Purpose:     declarations of time/date related classes (wxDateTime,
//              wxTimeSpan)
// Author:      Vadim Zeitlin
// Modified by:
// Created:     10.02.99
// RCS-ID:      $Id$
// Copyright:   (c) 1998 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

#ifndef _WX_DATETIME_H
#define _WX_DATETIME_H

#ifdef __GNUG__
    #pragma interface "datetime.h"
#endif

#include <time.h>
#include <limits.h>             // for INT_MIN

#include "wx/longlong.h"

class WXDLLEXPORT wxDateTime;
class WXDLLEXPORT wxTimeSpan;
class WXDLLEXPORT wxDateSpan;

// don't use inline functions in debug builds - we don't care about
// performances and this only leads to increased rebuild time (because every
// time an inline method is changed, all files including the header must be
// rebuilt)
#ifdef __WXDEBUG__
    #define inline
#endif // Debug

/*
 * TODO Well, everything :-)
 *
 * 1. Time zones with minutes (make wxTimeZone a class)
 * 2. getdate() function like under Solaris
 * 3. text conversion for wxDateSpan
 */

/*
  The three classes declared in this header represent:

  1. An absolute moment in the time (wxDateTime)
  2. A difference between two moments in the time, positive or negative
     (wxTimeSpan)
  3. A logical difference between two dates expressed in
     years/months/weeks/days (wxDateSpan)

  The following arithmetic operations are permitted (all others are not):

  addition
  --------

  wxDateTime + wxTimeSpan = wxDateTime
  wxDateTime + wxDateSpan = wxDateTime
  wxTimeSpan + wxTimeSpan = wxTimeSpan
  wxDateSpan + wxDateSpan = wxDateSpan

  substraction
  ------------
  wxDateTime - wxDateTime = wxTimeSpan
  wxTimeSpan - wxTimeSpan = wxTimeSpan
  wxDateSpan - wxDateSpan = wxDateSpan

  multiplication
  --------------
  wxTimeSpan * number = wxTimeSpan
  wxDateSpan * number = wxDateSpan

  unitary minus
  -------------
  -wxTimeSpan = wxTimeSpan
  -wxDateSpan = wxDateSpan
*/

// ----------------------------------------------------------------------------
// This class represents an absolute moment in the time
// ----------------------------------------------------------------------------

class WXDLLEXPORT wxDateTime
{
public:
    // types
    // ------------------------------------------------------------------------

        // a small unsigned integer type for storing things like seconds, days
        // of the week, &c. It should be at least short (i.e. not char) to
        // contain the number of milliseconds - it may also be 'int' because
        // there is no size penalty associated with it in our code, we don't
        // store any data in this format
    typedef unsigned short wxDateTime_t;

        // the timezones
    enum TZ
    {
        // the time in the current time zone
        Local,

        // zones from GMT (= Greenwhich Mean Time): they're guaranteed to be
        // consequent numbers, so writing something like `GMT0 + offset' is
        // safe if abs(offset) <= 12

        // underscore stands for minus
        GMT_12, GMT_11, GMT_10, GMT_9, GMT_8, GMT_7,
        GMT_6, GMT_5, GMT_4, GMT_3, GMT_2, GMT_1,
        GMT0,
        GMT1, GMT2, GMT3, GMT4, GMT5, GMT6,
        GMT7, GMT8, GMT9, GMT10, GMT11, GMT12,
        // Note that GMT12 and GMT_12 are not the same: there is a difference
        // of exactly one day between them

        // Universal Coordinated Time
        UTC = GMT0

        // TODO add symbolic names for TZ (EST, MET, ...)?
    };

        // the calendar systems we know about: notice that it's valid (for
        // this classes purpose anyhow) to work with any of these calendars
        // even with the dates before the historical appearance of the
        // calendar
    enum Calendar
    {
        Gregorian,  // current calendar
        Julian      // calendar in use since -45 until the 1582 (or later)

        // TODO Hebrew, Chinese, Maya, ... (just kidding) (or then may be not?)
    };

        // these values only are used to identify the different dates of
        // adoption of the Gregorian calendar (see IsGregorian())
        //
        // All data and comments taken verbatim from "The Calendar FAQ (v 2.0)"