Description:
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DateTime::diff() ist off by 3 days when year roll over

Test script:
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<?php
date_default_timezone_set('UTC');

$datetime1 = new DateTime('2015-01-01');
$datetime2 = new DateTime('2015-03-10');
$interval = $datetime1->diff($datetime2);

echo $interval->format('%y years %m months and %d days')."\n";


$datetime1 = new DateTime('2014-12-31');
$datetime2 = new DateTime('2015-03-10');
$interval = $datetime1->diff($datetime2);

echo $interval->format('%y years %m months and %d days')."\n";



$datetime1 = new DateTime('1951-12-31');
$datetime2 = new DateTime('2015-03-10');
$interval = $datetime1->diff($datetime2);

echo $interval->format('%y years %m months and %d days')."\n";

Expected result:
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0 years 2 months and 9 days
0 years 2 months and 10 days
63 years 2 months and 10 days

Actual result:
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0 years 2 months and 9 days
0 years 2 months and 7 days
63 years 2 months and 7 days