Can you add the Actual and Expected output please?

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
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Actually, I see what happens.

There is no bug.

Unlike Moscow and New_York, Novosibirsk changed GMT offsets between June 2nd,2015 and June 2nd, 2017.

Moscow:
Europe/Moscow  Sat Mar 26 23:00:00 2011 UT = Sun Mar 27 03:00:00 2011 MSK isdst=0 gmtoff=14400
Europe/Moscow  Sat Oct 25 21:59:59 2014 UT = Sun Oct 26 01:59:59 2014 MSK isdst=0 gmtoff=14400
Europe/Moscow  Sat Oct 25 22:00:00 2014 UT = Sun Oct 26 01:00:00 2014 MSK isdst=0 gmtoff=10800

(Last change was in 2014 to UTC+3)

New York
UTC+3

Novosibirsk:

Asia/Novosibirsk  Sat Mar 26 20:00:00 2011 UT = Sun Mar 27 03:00:00 2011 +07 isdst=0 gmtoff=25200
Asia/Novosibirsk  Sat Oct 25 18:59:59 2014 UT = Sun Oct 26 01:59:59 2014 +07 isdst=0 gmtoff=25200
Asia/Novosibirsk  Sat Oct 25 19:00:00 2014 UT = Sun Oct 26 01:00:00 2014 +06 isdst=0 gmtoff=21600
Asia/Novosibirsk  Sat Jul 23 19:59:59 2016 UT = Sun Jul 24 01:59:59 2016 +06 isdst=0 gmtoff=21600
Asia/Novosibirsk  Sat Jul 23 20:00:00 2016 UT = Sun Jul 24 03:00:00 2016 +07 isdst=0 gmtoff=25200

UTC+6 in 2015, and UTC+7 in 2017. That's why you get the 3600 seconds difference.

Because of this, the method works incorrectly "diff" from "DateTime class"
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Из-за этого неверно работает метод "diff" класса DateTime


//correct:
$dataTimeZone = new DateTimeZone("Europe/Moscow");
    $datetime = new DateTime('02.06.2015',$dataTimeZone);
    $now = new DateTime('02.06.2017',$dataTimeZone);
    $interval = $datetime->diff($now);
    $fullYear = (int)$interval->format("%Y");
echo $fullYear;
// 2 - its correct

//incorrect
$dataTimeZone = new DateTimeZone("Asia/Novosibirsk");
    $datetime = new DateTime('02.06.2015',$dataTimeZone);
    $now = new DateTime('02.06.2017',$dataTimeZone);
    $interval = $datetime->diff($now);
    $fullYear = (int)$interval->format("%Y");
echo $fullYear;
// 1 - its incorrect

The diff method works pretty well, you are only looking at a fraction of the result though.

When you look at https://3v4l.org/6eiD6 you will notice that the difference is 1 year, 11 months, 30 days and 23 hours. Due to the DST-change it's 1 hour short of being two years!

But in fact diff does not provide the data correctly. Maybe need to fix the problem at the level of the environment?
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Но фактически diff предоставляет  неверные данные. Может быть нужно исправлять проблему на уровне окружения?

Why do you think the diff doesn't provide the data correctly? After all there IS one hour missing in the diff. 

You might want something different from it but that's a different story. The difference between anytime on the 2nd of June 2015 in "Asia/Novosibirsk" and the same time on the 2nd of June 2017 in Asia/Novosibirsk is 1 year, 11 months, 30 days and 23 hours. 

So I'd really be interested why you think it doesn't "provide the data correctly"

Because regardless of the time zone in the period beetween from 02.06.2015 to 02.06.2017  should be the same number of seconds. This is an axiom. No?
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Потому что независимо от часового пояса в промежутке от 02.06.2015 до 02.06.2017 должно быть одинаковое количество секунд. Это аксиома.

No. It's not. Due to the Timezone change there where about 3600 seconds less than you are expecting…