How to change the output field date in a view?
If you are asking for the how to get year from date and use the year in view query alter then 

You can use strtotime();

$year = date('Y', strtotime($field_data_field_issuu_date.field_issuu_date_value));


Another way in view you can use custom date format on display and show only year and use that value.(Depends on requirement)