How do I select records less than 1 year old?

This should be a fairly simple question but I know very little about SQL. I have a database which has the following fields:

• client_id
• scheduled_amount
• deposit_amount
• message_code_id
• note_text
• system_date

Now I wish to select all the records that are less than 1 year old from when the SQL statement is run. I know I should use DateDiff, anyone got any ideas?

Thanks