Customize date display format? Is it possible to customize the format in which Android displays the current date?

I'm interested mainly in:


the date format at the top on screen when pulling down the notification menu (currently for me, it's "DD/MM/YYYY")
The date format at the lock screen (currently for me, it's "Weekday, D Month")


I would like to have all dates displayed in ISO 8601 format, YYYY-MM-DD. The global date format can be changed from settings, but the only available options are MM/DD/YYYY, DD/MM/YYYY and YYYY/MM/DD, and it seems there's no way to define a completely custom date format or set - as a custom field separator. This also doesn't affect the lock screen.

I'm using a rooted Android 2.2 (Froyo) with Samsung TouchWiz 3.0. I'm also insterested in answers that require CyanogenMod or other custom ROMs.
The Notification Bar uses the global date format. So, just switch to the desired format from Settings ~> Date and time ~> Select Date Format.

For the lock screen, use a lock screen app. Search the Play Store, you can find many.