Random time and date between 2 date values

Question

I'm trying to write a php script (or line of code) to echo a random time and date between 2 dates, eg

2012-12-24 13:03

which would be between my chosen dates of 1st October 2012 and 1st Jan 2013.

Any ideas how best to do this? Thanks in advance.

Answer 1

Easy :) Just choose 2 random dates, convert to EPOCH, and random between these 2 values :)

EPOCH - The time since 1/1/1970, in seconds.
You can use the strtotime() function to make date-strings turn into epoch time, and the date() function to make it the other way back.

function rand_date($min_date, $max_date) {
    /* Gets 2 dates as string, earlier and later date.
       Returns date in between them.
    */

    $min_epoch = strtotime($min_date);
    $max_epoch = strtotime($max_date);

    $rand_epoch = rand($min_epoch, $max_epoch);

    return date('Y-m-d H:i:s', $rand_epoch);
}

Answer 2

You probably want to define a resolution, for example one minute, or three minutes or 15 seconds or one and a half day or what not. The randomness should be applied on the whole period, I've choosen one minute here for exemplary purposes (there are 132480 minutes in your period).

$start    = new Datetime('1st October 2012');
$end      = new Datetime('1st Jan 2013');
$interval = new DateInterval('PT1M'); // Resolution: 1 Minute
$period   = new DatePeriod($start, $interval, $end);
$random   = new RandomIterator($period);

list($result) = iterator_to_array($random, false) ? : [null];    

This for example gives:

class DateTime#7 (3) {
  public $date =>
  string(19) "2012-10-16 02:06:00"
  public $timezone_type =>
  int(3)
  public $timezone =>
  string(13) "Europe/Berlin"
}

You can find the RandomIterator here. Without it, it will take a little longer (ca. 1.5 the number of iterations compared to the example above) using:

$count    = iterator_count($period);
$random   = rand(1, $count);

$limited = new LimitIterator(new IteratorIterator($period), $random - 1, 1);
$limited->rewind();
$result = $limited->current();

I also tried with seconds, but that would take quite long. You probably want first to find a random day (92 days), and then some random time in it.

Also I've run some tests and I could not find any benefit in using DatePeriod so far as long as you're on common resolutions like seconds:

$start    = new Datetime('1st October 2012');
$end      = new Datetime('1st Jan 2013');

$random   = new DateTime('@' . mt_rand($start->getTimestamp(), $end->getTimestamp()));

or minutes:

/**
 * @param DateTime $start
 * @param DateTime $end
 * @param int|DateInterval $resolution in Seconds or as DateInterval
 * @return DateTime
 */
$randomTime = function (DateTime $start, DateTime $end, $resolution = 1) {

    if ($resolution instanceof DateInterval) {
        $interval   = $resolution;
        $resolution = ($interval->m * 2.62974e6 + $interval->d) * 86400 + $interval->h * 60 + $interval->s;
    }

    $startValue = floor($start->getTimestamp() / $resolution);
    $endValue   = ceil($end->getTimestamp() / $resolution);
    $random     = mt_rand($startValue, $endValue) * $resolution;

    return new DateTime('@' . $random);
};

$random = $randomTime($start, $end, 60);

Answer 3

Assuming you want to include October 1st, but not include Jan 1st...

$start = strtotime("2012-10-01 00:00:00");
$end =  strtotime("2012-12-31 23:59:59");

$randomDate = date("Y-m-d H:i:s", rand($start, $end));

echo $randomDate;