Random PHP dates

random_date.php

<?php
/**
 * Generates a random date.
 *
 * Essentially generates a random, positive integer and interprets it as a
 * number of seconds from the start of the UNIX epoch (i.e.: 1970-01-01 00:00:00
 * UTC).
 *
 * This function checks $min and $max: if you try to pass $min < 0, the function
 * will use 0 as the minimum; likewise, if you pass $max > getrandmax(), the
 * function will use getrandmax() as the maximum.
 *
 * @param int $min
 *   The smallest datetime we should generate (in UNIX time). If you pass a
 *   number less than 0, it will be automatically corrected to 0. If you run
 *   this function on a system where getrandmax() will return a number
 *   sufficiently high that it will be after the current UNIX timestamp, then
 *   you can set this argument to the value of time() and $max = NULL (or $max =
 *   getrandmax()) to generate a date in the future.
 * @param int|null $max
 *   The largest datetime we should generate, or NULL to use the value of
 *   getrandmax(). If you pass a number greater than getrandmax(), it will
 *   automatically be corrected to 0. Set this to the current value of time()
 *   and $min = 0 to generate a date in the past.
 *
 * @return \DateTime
 *   A datetime object representing this random date.
 */
function randomDatetime($min = 0, $max = NULL) {
  // Don't generate a date before the start of the UNIX epoch.
  $min = (int) $min;
  $min = ($min < 0) ? 0 : $min;

  // We can't generate a random integer bigger than getrandmax().
  $rand_max = getrandmax();
  if (is_null($max) || $max >= $rand_max) {
    $max = $rand_max;
  }
  else {
    $max = (int) $max;
  }

  $random_seconds_since_epoch = rand($min, $max);

  $answer = new DateTime();
  $answer->setTimestamp($random_seconds_since_epoch);

  return $answer;
}

/**
 * Generates a random date in the future.
 *
 * Note this function makes the assumption that getrandmax() will return a
 * number sufficiently high that it will be after the current UNIX timestamp.
 *
 * @return \DateTime
 *   A datetime object representing this random date.
 */
function randomDatetimeInFuture() {
  $current_datetime = time();
  $rand_max = getrandmax();
  return randomDatetime($current_datetime, $rand_max);
}

/**
 * Generates a random date in the past.
 *
 * @return \DateTime
 *   A datetime object representing this random date.
 */
function randomDatetimeInPast() {
  $current_datetime = time();
  return randomDatetime(0, $current_datetime);
}