countdown formatter

/*
  convdate.c -

  Tamara Temple <tamara@tamaratemple.com>
  Time-stamp: <2012-06-21 02:22:57 tamara>
  Created: 2012-06-21
  Copyright (c) 2011 Tamara Temple Web Development
  License: GPLv3

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.


*/

#include <stdio.h>
#include <time.h>

int main(int argc, char *argv[])
{
  struct tm tm;
  time_t t;
  time_t now;
  long left, weeks, days, hours, minutes, seconds;

  if (argc < 3) {
    printf("Usage: %s <format> <time_string>\n",argv[0]);
    return 1;
  }


  strptime(argv[2],argv[1],&tm);
  t=mktime(&tm);
  time(&now);

  left=(long) t - (long) now;
  if (left < 0) {
    printf("Deadline past.\n");
    return 2;
  }

  weeks = left/(60*60*24*7);
  days = (left%(60*60*24*7))/(60*60*24);
  hours = (left%(60*60*24))/(60*60);
  minutes = (left%(60*60))/(60);
  seconds = left%(60);


  printf("%d week(s), %d day(s), %d hour(s), and %d minute(s) left\n",weeks, days, hours, minutes, seconds);

  return 0;
}