Collection: filter by created_at by local time zone? (or CreatedAtStoreDate) - magento

Question

I have to filter a collection (invoice) by date to get all invoices of one month.
For example: the create_at date of one invoice (in database) is: 2014-04-30 22:27:30
If I filter the collection:
$dateFrom = '2014-04-01 00:00:00';
$dateTo = '2014-04-30 23:59:59';
$invoiceCollection->addAttributeToFilter('created_at', array(
'from' => $dateFrom,
'to' => $dateTo,
));
The invoice with this date will be in the collection.
There exists two kinds of dates:
$invoice->getCreatedAt()
And:
$invoice->getCreatedAtStoreDate()
In this case:
$invoice->getCreatedAt() = 2014-04-30 22:27:30 (UTC/GMT time)
$invoice->getCreatedAtStoreDate() = 2014-05-01 00:27:40 (local timezone)
Under Sales->Invoices "my" invoice will be collect under May. If I use
$invoiceCollection = Mage::getModel('sales/order_invoice')->getCollection();
the invoice is in "April".
So I have to filter my collection by CreatedAtStoreDate - but this is not a database-field.
My question:
How can I filter the order or invoice collection by CreatedAtStoreDate, so that the invoice or order with the date 2014-04-30 22:27:30 will be NOT in my April-Collection but in May?
Thanks for help.

Answer 1

You can use some GET param to define local offset, then add this offset to dates in filter. It will something like this (I didn't test it):
/**
* GET param which allow to set offset between local and server timezone. Server timezone is GMT.
* Examples: add ?gmt=2 in URL for set local time to GMT+2, ?gmt=-5 for GMT-5, etc.
*/
$gmt_offset = (int)Mage::app()->getRequest()->getParam('gmt');
$dateFrom = '2014-04-01 00:00:00';
$dateTo = '2014-04-30 23:59:59';
if($gmt_offset > -13 && $gmt_offset < 15 && $gmt_offset != 0){
$locale = Mage::app()->getLocale()->getLocaleCode();
$date_from = new Zend_Date(strtotime($dateFrom), Zend_Date::TIMESTAMP, $locale);
$date_to = new Zend_Date(strtotime($dateTo), Zend_Date::TIMESTAMP, $locale);
if($gmt_offset > 0){
$date_from->add($gmt_offset, Zend_Date::HOUR);
$date_to->add($gmt_offset, Zend_Date::HOUR);
}else{
$date_from->sub($gmt_offset, Zend_Date::HOUR);
$date_to->sub($gmt_offset, Zend_Date::HOUR);
}
$dateFrom = $date_from->get('YYYY-MM-dd HH:mm:ss');
$dateTo = $date_to->get('YYYY-MM-dd HH:mm:ss');
}
$invoiceCollection->addAttributeToFilter('created_at', array(
'from' => $dateFrom,
'to' => $dateTo,
));