Calculating the Zodiac Sign from the Birth Date

In astrology *myths*, zodiac is a belt of twelve constellations (sun, moon, and major planets) through which the Sun's path in the sky, the ecliptic, passes. The word zodiac comes from the Greek 'zodiakos,' literally meaning 'circle of animals.'

Calculating the Zodiac Sign from the Birth Date

The ZodiacSign function will return the name of the zodiac sign for a given date value.

//Returns the zodiac sign from a birth date
function ZodiacSign(const dateOfBirth: TDate): string;
type
  TZodiacSign = record
    Name : string;
    Day : integer;
  end;

const
  ZodiacSigns : array[1..12] of TZodiacSign =
  (
    (Name : 'Aquarius'; Day : 50), // "Water-bear" ends 02/19
    (Name : 'Pisces'; Day : 79), // "Fish" ends 03/20
    (Name : 'Aries'; Day : 110), // "Ram" ends 04/20
    (Name : 'Taurus'; Day : 131), // "Bull, ends 05/21
    (Name : 'Gemini'; Day : 172), // "Twins" ends 06/21
    (Name : 'Cancer'; Day : 203), // "Crab" ends 07/22
    (Name : 'Leo'; Day : 233), // "Lion" ends 08/21
    (Name : 'Virgo'; Day : 266), // "Virgin" ends 09/23
    (Name : 'Libra'; Day : 296), // "Scale", ends 10/23
    (Name : 'Scorpio'; Day : 326), // "Scorpion" ends 11/22
    (Name : 'Sagittarius'; Day : 357), // "Archer" ends 12/22
    (Name : 'Capricorn'; Day : 385) // "Sea-goat" ends 01/20
  ) ;
var
  d : word;
  idx : integer;
begin
  d := DayOfTheYear(dateOfBirth) ;

  if (d > 59) AND IsLeapYear(YearOf(dateOfBirth)) then Inc(d) ;
  if (d < 21) then d := d + DaysInYear(dateOfBirth) ;

  for idx := 1 to 12 do
  begin
    if d <= ZodiacSigns[idx].Day then
    begin
      result := ZodiacSigns[idx].Name;
      exit;
    end;
  end;
end; (*ZodiacSign*)

Note: The key functions used here are: IsLeapYear, DaysInYear and DayOfTheYear. When you figure out what is their job in the "ZodiacSign" function, do let me know ;)

A hint ... for example: for "Leo", Day 233 is the day of the year (a non leap year) for August 21 - ending day for the Leo sign.

Usage:

var
  dob : TDateTime;
begin
  dob := EncodeDate(1973, 1, 29) ;

  //will return aquarius
  ShowMessage(ZodiacSign(dob)) ;
end;

Note:

1. I have tested the code 99% :) Fell free to send any fixes you might find.

2. If you have some shorter code to get the zodiac sign out of a TDate value ... I would like to see it.

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