zdate.man

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               assert(date.AddWeeks(-1) == zDate(zDate::oct,4,1996));


   ZDATE::ADDYEARS
   --------------------------------------------------------------------------
     Synopsis  Adds or subtracts a number of years from a date.

     Syntax    zDate AddYears(int nYears) const;

     Remarks   This member function will add or subtract (if 'nYears' is
               negative) a number of years to the current date object and
               will return a new zDate with the resulting value. The calling
               object is not modified by this function. Note that when
               manipulating years, a date could become invalidated (such as
               adding 1 to a leap year will cause February 29 to be an
               invalid date). This routine takes that into account and will
               adjust itself accordingly (in the example above, the new date
               will be March 1). Care must be taken that years do not fall
               below 1 A.D.

     Return    A zDate object with the new date.

     See also  zDate::AddWeeks(); zDate::AddMonths(); zDate::operator+();

     Example   zDate date(zDate::feb, 29, 1996);
               assert(date.AddYears(-2) == zDate(zDate::mar,1,1994));


   ZDATE::AGE
   --------------------------------------------------------------------------
     Synopsis  Returns the age of someone with a specific birthrate
               (for current date object).

     Syntax    int Age(const zDate &BirthDay) const;

     Remarks   This routine calculates the age of a person with a birthday
               date of 'BirthDay'. This function does not modify the calling
               object. Care must be taken that the calling object is greater
               than BirthDay (i.e. that the person has already been born).

     Return    The age (in years) of the person.

     See also  zDate::operator-()

     Example   zDate brani(zDate::jul, 16, 1973);
               cout << "I am " << Today().Age(brani) << " years old";


   ZDATE::BEGINDST
   --------------------------------------------------------------------------
     Synopsis  Calculates the beginning date of the Daylight Savings Time.

     Syntax    zDate BeginDST() const;
               static zDate BeginDST(int aYear);

     Remarks   There are two version of this function. The first one returns
               the date of the beginning of DST for the year of the current
               date object. The second one is more generic as it returns the
               start of DST for any year. These routine do not modify
               anything, they simply return a zDate object with the date
               when the DST comes into effect. By default, the routines will
               use the USA standard for DST calculations. In the US, DST
               begins at 2:00am on the first Sunday of April and ends at
               2:00am on the last Sunday of October. You can modify these
               rules by using the SetBeginDST() and SetEndDST() member
               functions.

     Return    The date when DST will come into effect.

     See also  zDate::EndDST(); zDate::IsDST(); zDate::SetBeginDST()

     Example   assert(zDate::BeginDST(1996)==zDate(zDate::apr,7,1996))


   ZDATE::DAY
   --------------------------------------------------------------------------
     Synopsis  Returns the day of month of the current date object.

     Syntax    int Day() const;

     Remarks   This routine return the current day of the month. Days start
               from 1 and can go up to 31, depending on the current day.
               Note that there are no days between October 4 and October 15,
               1582 (this is when Pope Gregor XIII canceled them).

     Return    The day of the month.

     See also  zDate::Month(); zDate::Year(); zDate::DayOfWeek();

     Example   cout << "Today is the " << zDate::Today().Day()
                    << "th day of the month";


   ZDATE::DAYNUMBER
   --------------------------------------------------------------------------
     Synopsis  Returns the day number (from January 1, 1) for the object.

     Syntax    ulong DayNumber() const;

     Remarks   This returns the day number of the date object. Day numbering
               begins with January 1, 0001 A.D. being day 1 and so on. As
               such, these day numbers are not Julian dates (which begin
               several thousand years B.C.). Leap years are taken into
               account as well as the Gregorian reform (with the standard
               date of October 4, 1582)

     Return    The day number (unsigned long integer).

     See also  zDate::zDate(ulong nDayNumber);

     Example   cout << "Today is the " << zDate::Today().DayNumber()
                    << "th day of the year.";


   ZDATE::DAYOFWEEK
   --------------------------------------------------------------------------
     Synopsis  Returns the day of the week for the date object.

     Syntax    week_day DayOfWeek() const;

     Remarks   This returns the day of the week for the current date object.
               You must use the week_day enumeration to interpret the return
               value of this function. When trying to access the week_day
               constants, be sure to use the scope resolution operator.

     Return    The day of the week.

     See also  zDate::week_day;

     Example   assert(zDate::sat == zDate(zDate::oct,5,1996).DayOfWeek());


   ZDATE::DAYOFYEAR
   --------------------------------------------------------------------------
     Synopsis  Returns the day of the year from January 1.

     Syntax    int DayOfYear() const;

     Remarks   This member function returns the day of the year for the
               current object. The day numbering starts from January 1 for
               the same year being the first day. The current day number
               will depend on whether the year is leap or not too. The range
               of possible values is 1..366 (or 365 for non-leap years),
               with the upper limit being December 31.

     Return    The day number.

     See also  zDate::DayOfWeek(); zDate::DayNumber();

     Example   assert(366 == zDate(zDate::dec,31,2000).DayOfYear());


   ZDATE::DAYSINMONTH
   --------------------------------------------------------------------------
     Synopsis  Returns the number of days for a specific month in a year.

     Syntax           int DaysInMonth() const;
               static int DaysInMonth(month aMonth, int aYear);

     Remarks   These two versions of the function will return the number of
               days for a specific month. The first version will return the
               number of days in the month of the date object that called it;
               while the second version can be used without an actual zDate
               object and returns the number of days for a month of a year
               you specify. Note that October 1582 had only 21 days as a
               result of the reform of Pope Gregor XIII.

     Return    The number of days in a month.

     See also  zDate::DaysInYear(); zDate::IsLeapYear();

     Example   assert( 28 == zDate::DaysInMonth(zDate::feb, 1995) );


   ZDATE::DAYSINYEAR
   --------------------------------------------------------------------------
     Synopsis  Returns the number of days in a specific year.

     Syntax           int DaysInYear() const;
               static int DaysInYear(int aYear);

     Remarks   The first version of this routine returns the number of days
               in the year of the current date object. The second version
               can be used without instantiating an actual object and returns
               the number of days in any year. There are two possible values
               365 and 366 depending on whether the year is leap or not
               (except for 1582 which lost 10 days). These functions do not
               modify any objects.

     Return    The number of days in a year.

     See also  zDate::DaysInMonth(); zDate::IsLeapYear();

     Example   assert( 366 == zDate::DaysInYear(1996) );


   ZDATE::EASTER
   --------------------------------------------------------------------------
     Synopsis  Return the date of Easter for any given year.

     Syntax           zDate Easter() const;
               static zDate Easter(int year);

     Remarks   This routine returns the date for Easter for any given year
               (the second version) or for the year of the calling zDate
               object. It uses some obscure algorithm to calculate the
               ecclesiastical Easter (which is the same for all countries
               regardless of where they are) and is different from the
               astronomical date (which does not mean much anyway). Easter is
               sometimes said to be the first Sunday that occurs after the
               full moon that follows the vernal equinox (March 22). This
               means the Easter can vary between March 22 and April 25. This
               is an over-simplification as the Church does not actually use
               astronomical observations of the Moon but rather, it has
               constructed its own calendar of Easter days which it uses.
               This function is a very presentable approximation. For more
               information, read one of the Almanacs or visit the US Naval
               Observatory. They have tons of nice information there,
               including an even more obfuscated formula for calculating the
               Easter date.

     Return    A zDate object with the Easter date.

     See also  zDate::MoonPhase(); zDate::DayOfWeek()

     Example   zDate Easter(zDate::apr, 7, 1996);
               assert( Easter == zDate::Easter(1996) );


   ZDATE::ENDDST
   --------------------------------------------------------------------------
     Synopsis  Return the date when the Daylight Savings Time is ended.