text: /*
   * Copyright (c) 2012-2015 Christian Hansen <chansen@cpan.org>
   * <https://github.com/chansen/c-dt>
   * All rights reserved.
   * 
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met: 
   * 
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer. 
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution. 
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  #include <stddef.h>
  #include "dt_core.h"
  
  dt_t
  dt_start_of_year(dt_t dt, int offset) {
      int y;
      dt_to_yd(dt, &y, NULL);
      return dt_from_yd(y + offset, 1);
  }
  
  dt_t
  dt_start_of_quarter(dt_t dt, int offset) {
      int y, q;
      dt_to_yqd(dt, &y, &q, NULL);
      return dt_from_yqd(y, q + offset, 1);
  }
  
  dt_t
  dt_start_of_month(dt_t dt, int offset) {
      int y, m;
      dt_to_ymd(dt, &y, &m, NULL);
      return dt_from_ymd(y, m + offset, 1);
  }
  
  dt_t
  dt_start_of_week(dt_t dt, dt_dow_t first) {
      return dt - (dt_dow(dt) - first + 7) % 7;
  }
  
  dt_t
  dt_end_of_year(dt_t dt, int offset) {
      int y;
      dt_to_yd(dt, &y, NULL);
      return dt_from_yd(y + offset + 1, 0);
  }
  
  dt_t
  dt_end_of_quarter(dt_t dt, int offset) {
      int y, q;
      dt_to_yqd(dt, &y, &q, NULL);
      return dt_from_yqd(y, q + offset + 1, 0);
  }
  
  dt_t
  dt_end_of_month(dt_t dt, int offset) {
      int y, m;
      dt_to_ymd(dt, &y, &m, NULL);
      return dt_from_ymd(y, m + offset + 1, 0);
  }
  
  dt_t
  dt_end_of_week(dt_t dt, dt_dow_t first) {
      return dt + (first - dt_dow(dt) + 6) % 7;
  }
  
  