Your conversion "to" a rental is not in question here. With your mention of the last renter moving out on Jan 31 2019, that indicates to me they were in there well before Jan 1 of 2019. Do your "days rented" count starts on Jan 1st 2019.
Your data converted to personal use must be at least the day you started moving in. I like to "play it safe" and make it one day before I started moving in.
For a typical person whose intent is to convert it to personal use once the last renter moves out, the date of conversion to personal use would be one day after the renter moved out. But your intent was to rent it out again, and that didn't work out. So make y our date of conversion the day before you moved in. You could also make it one day after you pulled all advertising for it too, if you want.
Me personally, I'd convert it the day after the last renter moved out because I want to stop depreciation as soon as possible.
As for the advertising, things must be different in your location. Where I live in FL hardly nobody pays anyone anything to "advertise" their rental property. At most, I might advertise in one of the free "swip-swap" groups on facebook. But for the most part, I just stick a "For Rent" sign in the front yard in the morning, and if it's a weekend I'll have calls coming in by lunchtime.
Now I have three rentals of which only two are classified as such right now. (Daughter living in one temporarily, after divorce). I will on average go through 7 applicants before I find one I am comfortable with as a tenant, and they are comfortable with me as a landlord. You wouldn't believe some of the scams I've had folks try to pull on me over the 30 plus years I've been a landlord.
