75 lines
2.7 KiB
C++
75 lines
2.7 KiB
C++
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// This may look like C code, but it is really -*- C++ -*-
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// ------------------------------------------------------------------
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// The Goldware Library
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// Copyright (C) 1990-1999 Odinn Sorensen
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// Copyright (C) 1999-2000 Alexander S. Aganichev
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// ------------------------------------------------------------------
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this program; if not, write to the Free
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// Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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// MA 02111-1307, USA
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// ------------------------------------------------------------------
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// $Id$
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// ------------------------------------------------------------------
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// Julian date conversion functions.
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// ------------------------------------------------------------------
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#include <gtimall.h>
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// ------------------------------------------------------------------
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inline int isleap(unsigned yr) { return yr % 400 == 0 || (yr % 4 == 0 && yr % 100 != 0); }
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inline unsigned months_to_days(unsigned month) { return (month * 3057 - 3007) / 100; }
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inline long years_to_days(unsigned yr) { return yr * 365L + yr / 4 - yr / 100 + yr / 400; }
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// ------------------------------------------------------------------
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long YMD2JDN(unsigned yr, unsigned mo, unsigned day) {
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long scalar;
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scalar = day + months_to_days(mo);
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if(mo > 2) /* adjust if past February */
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scalar -= isleap(yr) ? 1 : 2;
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yr--;
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scalar += years_to_days(yr);
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return scalar - 693595L;
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}
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// ------------------------------------------------------------------
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void JDN2YMD(long scalar, unsigned *yr, unsigned *mo, unsigned *day) {
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scalar += 693595L;
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unsigned n; /* compute inverse of years_to_days() */
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for(n = (unsigned)((scalar * 400L) / 146097L); years_to_days(n) < scalar;)
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n++; /* 146097 == years_to_days(400) */
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*yr = n;
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n = (unsigned)(scalar - years_to_days(n-1));
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if(n > 59) { /* adjust if past February */
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n += 2;
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if(isleap(*yr))
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n -= n > 62 ? 1 : 2;
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}
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*mo = (n * 100 + 3007) / 3057; /* inverse of months_to_days() */
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*day = n - months_to_days(*mo);
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}
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// ------------------------------------------------------------------
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