PHP and the end of October

Question

I have found the weirdest error. And I'm not asking for a fix, I'm just curious if you guys experienced the same and leave it for future reference.

I have the following code, which should output every day of the year 2016

$day = "2016-01-01";
for($i = 1; $i<= 365; $i++){
  $day = date("Y-m-d", strtotime($day)+60*60*24);
  echo $day."<br/>";    
}

But after 30-10-2016 it stops increasing and displays the same date.

PHP Version is 5.6.22. This happens for every year, not only 2016. Any idea what is causing this? Is this a problem with this specific PHP Version? Is this a timezone problem? Have you experienced the same, or something similar?

What interests me is the cause of this problem. There seems to be something wrong with the strtotime function.

Answer 1

Adding seconds to timestamps to change days/weeks/months can have unexpected results. Try explicitly adding one day...

$day = "2016-01-01";
for($i = 1; $i<= 365; $i++){
   $day = date("Y-m-d", strtotime("+ 1 day", strtotime($day)));
   echo $day.PHP_EOL;    
}

Which timezone is your PHP set to, is there a daylight savings time change at the end of October? - That will cause the date to stick as the day may be 25 hours long.