How to get the raw 'created_at' value in the database (not an object cast to an ActiveSupport::TimeWithZone)
use attributes_before_type_cast
Post.find(23).attributes_before_type_cast["created_at"]
or
Post.find(23).read_attribute_before_type_cast("created_at")
Edit
You can call like this also:
Post.find(23).created_at_before_type_cast
according to Accessing attributes before they have been typecasted.