As for the specific date you requested, if you plan to prepare your return online, Online TurboTax for 2019 opened on December 4.
The 2019 desktop TurboTax (CD/download) became available in mid-November.
You could have already been entering your data. Be aware that just like every year there will be a lot of revisions to the product over the next few weeks as new tax laws and new tax forms become available. But you can start entering things.