how to calculate a difference between two Zend_Date objects, in months

Question

I have two objects of Zend_Date class and I want to calculate the difference between them in full calendar months.. How can I do this?

<?php
$d1 = new Zend_Date('1 Jan 2008');    
$d2 = new Zend_Date('1 Feb 2010');
$months = $d1->sub($d2)->get(Zend_Date::MONTH);
assert($months == -25); // failure here

Thanks in advance!

Answer 1

With the help of Zend_Measure_Time you can easily get any difference you want:

    $timeNow = new Zend_Date();
    $timeThen = new Zend_Date("2011-05-21T10:30:00");
    $difference = $timeNow->sub($timeThen);

    $measure = new Zend_Measure_Time($difference->toValue(), Zend_Measure_Time::SECOND);
    $measure->convertTo(Zend_Measure_Time::MONTH);

    echo $measure->getValue();

No need for complicated calculations!