根据日期获取bigcommerce商店的产品？

Question

我想根据日期使用api在我的Bigcommerce商店中获得一些产品。所以我遵循了以下api代码。但没有运气

$filter = array('date_created' => 'Sat, 25 Jan 2014 16:43:15 +0000');//query filter

$products = Bigcommerce::getProducts($filter);

But in the same way following one is working good.

$filter = array('sku' => 'CST-120');//query filter

$products = Bigcommerce::getProducts($filter);

所以请任何帮助我如何更改日期变量会更好