"Nothing has changed" - Determining when a procedure has been altered

Someone need to determine when a stored procedure was last altered. Without having implemented a series of DDL triggers, how can this be accomplished?

In Microsoft SQL Server, you can easily retrieve this information from the sys.procedures catalog view. The following query demonstrates this.

SELECT
[name]
,modify_date
,create_date
,*
FROM
sys.procedures

Of course you can take it a step further by limiting the results to a period of time where you know that no changes should have been made. For example, the following query lists all stored procedures that have been changed since August 1, 2007 (the time I last visited this client).

SELECT
[name]
,modify_date
,create_date
,*
FROM
sys.procedures
WHERE
modify_date > '2008-10-01'

Although, using this technique will not allow me to identify who made the change, I can at least determine that a change has taken place.
Cheers!