Don't ask me how to do this exactly, but off the top of my head it wouldn't be too hard. You'll just need to make use of the PHP date() function and blend it in with the donation script. Then you'd add a new DB table, and store the date there.
From there you can simply use a query to access and display the date in any script you want. =) Maybe in global.php so it's accessable forum-wide. If you're an intermidiate PHP/MySQL coder this shouldn't be too hard, unless there's something else I don't know about. (I haven't looked at the donation script code you see.

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