Any time a product is updated and saved, its "created_at" entry in the "catalog_product_entity" database table is updated to the format YYYY-DD-MM, but it should keep it as YYYY-MM-DD. The date/time do not change, only the format. It isn't a big problem in itself, but it is creating problems when I attempt to sort products by creation date.
Here is an example:
- created_at before: 2015-04-10 13:21:09 (YYYY-MM-DD)
- edit and save product via Magento
- created_at after: 2015-10-04 13:21:09 (YYYY-DD-MM)
Extra information: It is a Magento 1.9.1 store with the locale set to English (US) and timezone set to Los Angeles. The products from the store were originally imported via Magento's Import/Export feature from a wooCommerce store. Let me know if you need any more info.