headers/private/shared/Holiday.h

   1 /*
   2  * Copyright 2010, Haiku, Inc. All Rights Reserved.
   3  * Distributed under the terms of the MIT License.
   4  */
   5 #ifndef _HOLIDAY_H_
   6 #define _HOLIDAY_H_
   7
   8
   9 #include <DateTime.h>
  10
  11
  12 namespace BPrivate {
  13
  14
  15 class BHoliday {
  16 public:
  17         virtual                                         ~BHoliday() { };
  18 };
  19
  20
  21 class BEasterHoliday : public BHoliday {
  22 public:
  23         static  BDate                           EasterSunday(int32 year);
  24         static  BDate                           AscensionDay(int32 year);
  25         static  BDate                           PentecostDay(int32 year);
  26 };
  27
  28
  29 /*!
  30         Returns the date for easter sunday for the \c year.
  31 */
  32 /*static*/ BDate
  33 BEasterHoliday::EasterSunday(int32 year)
  34 {
  35         // http://bloggingabout.net/blogs/jschreuder/archive/2005/06/24/7019.aspx
  36         int32 gold = year % 19;
  37         int32 century = year / 100;
  38         int32 h = (century - (int32)(century / 4)
  39                 - (int32)((century * 8 + 13) / 25) + 19 * gold + 15) % 30;
  40         int32 i = h - (int32)(h / 28) * (1 - (int32)(h / 28)
  41                 * (int32)(29 / (h + 1)) * (int32)((21 - gold) / 11));
  42
  43         int32 day = i - ((year + (int32)(year / 4) + i + 2 - century
  44                 + (int32)(century / 4)) % 7) + 28;
  45         BDate date;
  46         if (day > 31)
  47                 date.SetDate(year, 4, day - 31);
  48         else
  49                 date.SetDate(year, 3, day);
  50         return date;
  51 }
  52
  53
  54 /*!
  55         Returns the date for ascension day for the \c year.
  56 */
  57 /*static*/ BDate
  58 BEasterHoliday::AscensionDay(int32 year)
  59 {
  60         BDate date = EasterSunday(year);
  61         date.AddDays(39);
  62         return date;
  63 }
  64
  65
  66 /*!
  67         Returns the date for pentecost day for the \c year.
  68 */
  69 /*static*/ BDate
  70 BEasterHoliday::PentecostDay(int32 year)
  71 {
  72         BDate date = EasterSunday(year);
  73         date.AddDays(49);
  74         return date;
  75 }
  76
  77
  78 }       // namespace BPrivate
  79
  80
  81 using BPrivate::BHoliday;
  82 using BPrivate::BEasterHoliday;
  83
  84
  85 #endif  // _HOLIDAY_H_