time/isLeap.c

   1 /*
   2  * (C)2012 Michael Duane Rice All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * Redistributions of source code must retain the above copyright notice, this
   9  * list of conditions and the following disclaimer. Redistributions in binary
  10  * form must reproduce the above copyright notice, this list of conditions
  11  * and the following disclaimer in the documentation and/or other materials
  12  * provided with the distribution. Neither the name of the copyright holders
  13  * nor the names of contributors may be used to endorse or promote products
  14  * derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /* $Id: isLeap.c 2325 2013-04-02 21:22:16Z swfltek $ */
  30
  31 /*
  32     Return 1 if 'year' is a leap year, else 0.
  33 */
  34
  35 #include <stdlib.h>
  36
  37 unsigned char
  38 is_leap_year(int year)
  39 {
  40     div_t           d;
  41
  42     /* year must be divisible by 4 to be a leap year */
  43     if (year & 3)
  44         return 0;
  45
  46     /* If theres a remainder after division by 100, year is not divisible by 100 or 400 */
  47     d = div(year, 100);
  48     if (d.rem)
  49         return 1;
  50
  51     /* If the quotient is divisible by 4, then year is divisible by 400 */
  52     if ((d.quot & 3) == 0)
  53         return 1;
  54
  55     return 0;
  56 }