First of all, you need to have access to the file (the Notepad or Writer document, for example). Then you can have a look at the creation date or modification date using Windows Explorer or My Computer. But that's easy to manipulate also.
Then some programs might (just: might) keep the data somewhere inside the file also. MS Word in the property sheet of a document, displays date of creation, modification and opening of the document. But I don't know if it takes the first 2 from the file properties you see in Windows Explorer or if it maintains its own administration. That's easy to try, if you want to know it.
Hope this helps.
Is it possible to know the actual date in which a letter was written on a computer when somebody puts a date on a document far away back of the actual date the documento was written. Is it there in the hard drive or register the actual date?