How can I find out the dates when I filed tax return using Turbo Tax 2014, 2015 and 2016?

[DoninGA]

Look at the Postmark Report which is included in the PDF of the tax return for download.

To access your prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Download/print return (PDF)