Files
harbour-core/contrib/hbnf/easter.prg
Viktor Szakats cfb1dfd8fa 2013-04-08 00:52 UTC+0200 Viktor Szakats (harbour syenar.net)
* bin/check.hb
    + will now check for missing copyright/license message
      in source files (except for tests and files shorter
      than 20 lines)

  * contrib/hbamf/amf.h
  * contrib/hbamf/amfstdio.c
  * contrib/hbamf/hbamfobj.prg
  * contrib/hbamf/hbcls.c
  * contrib/hbgt/strasint.c
  * contrib/hbhttpd/core.prg
  * contrib/hbhttpd/widgets.prg
  * contrib/hbmisc/hbedit.prg
  * contrib/hbmisc/hbeditc.c
  * contrib/hbmisc/stringsx.c
  * contrib/hbmisc/udpds.prg
  * contrib/hbnf/aredit.prg
  * contrib/hbnf/easter.prg
  * contrib/hbnf/mouse1.prg
  * contrib/xhb/hbsyslog.c
  * extras/guestbk/_cgi.prg
  * extras/guestbk/_inifile.prg
  * extras/guestbk/cgi.ch
  * extras/hbdroid/hvminit.c
  * extras/hbdroid/msginfo.c
  * extras/hbusb/core.c
  * extras/hbvpdf/hbvpdf.ch
    + added copyright/license headers where missing

  * tests/inifiles.prg
    + synced with another copy

  * include/hbclass.ch
  * src/compiler/expropta.c
  * src/compiler/exproptb.c
  * src/macro/macroa.c
  * src/macro/macrob.c
    * minor cleanup
2013-04-08 00:53:37 +02:00

92 lines
2.4 KiB
Plaintext

/*
* Author....: Paul Tucker
* Email.....: <ptucker@sympatico.ca>
*
* While I can say that I wrote the program, the algorithm is from Donald
* Knuth's The Art of Computer Programming, Section 1.3.2. So, the source
* code is an original work by Paul Tucker and is placed in the public domain
*
* Modification history:
* ---------------------
*
* Rev 1.2 15 Aug 1991 23:05:28 GLENN
* Forest Belt proofread/edited/cleaned up doc
*
* Rev 1.1 14 Jun 1991 19:51:42 GLENN
* Minor edit to file header
*
* Rev 1.0 01 Apr 1991 01:01:16 GLENN
* Nanforum Toolkit
*
*/
FUNCTION ft_Easter( nYear )
LOCAL nGold, nCent, nCorx, nCorz, nSunday, nEpact, nMoon
LOCAL nMonth := 0, nDay := 0
IF HB_ISSTRING( nYear )
nYear := Val( nYear )
ENDIF
IF HB_ISDATE( nYear )
nYear := Year( nYear )
ENDIF
IF HB_ISNUMERIC( nYear )
IF nYear > 1582
// <<nGold>> is Golden number of the year in the 19 year Metonic cycle
nGold := nYear % 19 + 1
// <<nCent>> is Century
nCent := Int( nYear / 100 ) + 1
// Corrections:
// <<nCorx>> is the no. of years in which leap-year was dropped in order
// to keep step with the sun
nCorx := Int( ( 3 * nCent ) / 4 - 12 )
// <<nCorz>> is a special correction to synchronize Easter with the moon's
// orbit.
nCorz := Int( ( 8 * nCent + 5 ) / 25 - 5 )
// <<nSunday>> Find Sunday
nSunday := Int( ( 5 * nYear ) / 4 - nCorx - 10 )
// Set Epact <<nEpact>> (specifies occurance of a full moon)
nEpact := Int( ( 11 * nGold + 20 + nCorz - nCorx ) % 30 )
IF nEpact < 0
nEpact += 30
ENDIF
IF ( nEpact == 25 .AND. nGold > 11 ) .OR. nEpact == 24
++nEpact
ENDIF
// Find full moon - the <<nMoon>>th of MARCH is a "calendar" full moon
nMoon := 44 - nEpact
IF nMoon < 21
nMoon += 30
ENDIF
// Advance to Sunday
nMoon := Int ( nMoon + 7 - ( ( nSunday + nMoon ) % 7 ) )
// Get Month and Day
IF nMoon > 31
nMonth := 4
nDay := nMoon - 31
ELSE
nMonth := 3
nDay := nMoon
ENDIF
ENDIF
ELSE
nYear := 0
ENDIF
RETURN hb_SToD( Str( nYear, 4 ) + PadL( nMonth, 2, "0" ) + PadL( Int( nDay ), 2, "0" ) )