Selecting all records from one year ago till now

I'm having trouble with a query, or at leas finding the right function.

Google didn't do much help so I'll just ask it here:

I have a table filled with a lot of rows and I need to select all the rows that are less than a year old till now.

The table (called orders) has a DateTime column named order_date, that's the field that determines when the order was placed.

So: How can I select all the records that have an order_date between now and a full year ago?