Elapsed function stops working on end of months?

[Teach]

Hi guys.

 

I am using the following code:

 

// Between a past time and now:
// $elapsed_time = elapsed(strtotime('2004-05-19'));
// $elapsed_time = elapsed(strtotime('2004-05-19 13:12:11'));

// Between two times:
// $elapsed_time = elapsed(strtotime('2004-05-19'), strtotime('2008-11-20'));

// Between a future time and now:
// $elapsed_time = elapsed(strtotime('2008-11-20'));

// Between a past time and now, with seconds included in the return 'string 'element:
// $elapsed_time = elapsed(strtotime('2004-05-19'), null, 'seconds');
// With days minumum (not hours, minutes, or seconds) in the 'string':
// $elapsed_time = elapsed(strtotime('2004-05-19'), null, 'days');

function elapsed($start_ts, $now_ts = null, $min_period = 'minutes')
{
  $periods = array('years', 'months', 'days', 'hours', 'minutes', 'seconds');
  if (empty($now_ts)) {
    $now_ts = time();
  }
  $same = false;
  if ($now_ts == $start_ts) {
    $same = true;
  } elseif ($now_ts < $start_ts) {
    $tmp_ts = $now_ts;
    $now_ts = $start_ts;
    $start_ts = $tmp_ts;
  }
  $min_key = array_keys($periods, $min_period);
  $ret['string'] = '';
  foreach ($periods as $key => $period) {
    $ret[$period] = 0;
    if ($same) {
      continue;
    }
    while (($start_ts = strtotime('+1 ' . $period, $start_ts)) < $now_ts) {
      $ret[$period]++;
    }
    $start_ts = strtotime('-1 ' . $period, $start_ts);
    if ($key > $min_key[0]) {
      continue;
    }
    if ($ret[$period] !== 0) {
      $ret['string'] .= $ret[$period] . ' ' . $period;
      if ($ret[$period] === 1) {
        $ret['string'] = substr($ret['string'], 0, strlen($ret['string']) - 1);
      }
      $ret['string'] .= ', ';
    }
  }
  if (!$ret['string']) $ret['string'] = $ret['seconds'] . ' seconds'; 
  $ret['string'] = rtrim($ret['string'], ', ');
  return $ret;
}

 

To display how long ago something was (using the examples at the top of the code).

 

The problem is that on the end of certain months, for example today (Mon 31st March) it always returns 0 seconds, nothing else.

 

Any idea why that is, and if it's fixable? Apart from that it works like a dream

 

Thank you!