The TurboTax FAQ below instructs you on how to print/screenshot your "electronic postmark", which will verify the date and time of filing.
https://ttlc.intuit.com/replies/3301167
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***