I set up payment from my bank account. How do I find out which day I set the payment for?

It's one of the last questions they ask you.  When do you want the IRS to withdraw the funds, followed by the same question but for the state. I assume you are at the end so just go back a few pages and you will find what you entered.  Near the bottom of those pages.

If you didn't select a date for the tax to be debited, the program will default to April 18. Likewise your state will default to payment on the tax filing deadline, unless you choose an earlier date. @pamcaneva