If you take an original piece of work that is somehow dated to the copyright office to disprove anothers work as plagarism they will see the dated original as the original work..... such as sending yourself a piece of mail with the work inside of it and keep it sealed it will be taken as evidence..... or if you were to show that it was posted here at a certain time before another posted it.......

Once it is electronically dated or recorded the copyright to said piece of work is yours....