Description:
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When calculating the number of months between the 1st of februari and the 1st of march I espect it to return 1 month but it returns 0.

I first tought this had to do with the leap year but that doesn't have anything to do with it becouse it also happens for 2015.

 

Test script:
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<?php

$first = new \DateTime('2016-02-01 00:00:00', new \DateTimeZone('Europe/Amsterdam'));
$second = new \DateTime('2016-03-01 00:00:00', new \DateTimeZone('Europe/Amsterdam'));

$diff = $first->diff($second);

echo $diff->format('%m') . PHP_EOL;
// Expect: 1, got 0

$second->modify('+1 month');
$diff2 = $first->diff($second);

echo $diff2->format('%m') . PHP_EOL;
// Expect: 2, got 2