Is there a data entry for the date converted?
Yes. While I'm sure you are aware of the screen about 3 screens in with the selection for "I converted this property to personal use" and you selected it, you also have to work through each individual asset, one at a time, listed in the asset/depreciation section. For each asset on the screen for "I stopped using this asset in 2020" click YES. I think it's the next screen where you enter the date. Then on the "Special Handling Required?" Screen click YES. (If you click NO, then you are "forced" to enter sales information.)
If so what date do I select 12/31/19 (last rental day) or 1/1/20 first day of second home?
You can't enter a prior year date for this, on your 2020 tax return. So it has to be 1/1/2020 or after. Note that one day isn't going to make one iota of difference here. However, you 'WILL" be filing the SCH E for 2020 with zero rental income, zero rental expenses, and don't bother entering the mortgage interest, property taxes or insurance data on the SCH E for 2020. None of your rental expenses incurred in 2020 (if any) are deductible at all, anyway. (Depreciation may or may not be a different matter, and has nothing to do with rental expenses.)
How best to enter the conversion to personal use?
You ask, in a way that makes me think you have choices on this. You don't. When you enter your conversion date of 1/1/2020 on each asset, you're not asked for days rented, days personal use, or none of that. But you are correct in that you will *NEVER* select the option for "I did not rent or attempt to rent this property in 2020". If you select that, then you're "forced" to delete the SCH E, and you will lose all of your depreciation history and loss carry over history. If you do that, the absolutely only possible way to get it back, is to totally and completely delete your 2020 tax return and start all over from scratch, so you can re-import it from the 2019 tax return.
The property includes an asset that used the special depreciation allowance and it will not have reached its end of life as of the conversion.
That's why it's important to not do anything that will lose your depreciation history. What I'm not clear on, is if you are "IN FACT" showing the conversion of that SDA asset to personal use (just as you should be on all other assets) *AND* selecting YES on the "Special Handling Required?" screen.
