The trade date of a stock transaction is simple to remember because that is the day the transaction took place. When I first began stock trading, I didn't realize there was a difference between the trade date and the settlement date.
What can really get confusing is when you sell the stock before the settlement date even arrives.
Most day traders buy and sell a stock all in one day and trying to keep up with those records can be challenging and quite time consuming.
It all balances out in the end and makes sense once you understand how it all works, but it is very important to make sure you keep good records for tax purposes.