lib/datetime.c

   1 /* datetime.c - Module for common datetime function.  */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2008  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/lib/datetime.h>
  21
  22 static char *grub_weekday_names[] =
  23 {
  24   "Sunday",
  25   "Monday",
  26   "Tuesday",
  27   "Wednesday",
  28   "Thursday",
  29   "Friday",
  30   "Saturday",
  31 };
  32
  33 int
  34 grub_get_weekday (struct grub_datetime *datetime)
  35 {
  36   int a, y, m;
  37
  38   a = (14 - datetime->month) / 12;
  39   y = datetime->year - a;
  40   m = datetime->month + 12 * a - 2;
  41
  42   return (datetime->day + y + y / 4 - y / 100 + y / 400 + (31 * m / 12)) % 7;
  43 }
  44
  45 char *
  46 grub_get_weekday_name (struct grub_datetime *datetime)
  47 {
  48   return grub_weekday_names[grub_get_weekday (datetime)];
  49 }