How should I determine the date when the rental property is ready to rent?

[nestlen]

I lived in the apartment from Jan to early April and relocated to another city before it was rented out on May 7th. The apartment was empty between the time I left and tenant moved in (about 1 month), during which my agent posted AD for rent and had it clean up etc. 

My question is how should I determine when it was ready to rent? Can I use any date between the gap?  

[LindaA · Accepted solution]

You should use the date when the apartment was ready (i.e., clean) and available for someone to move in. Page 6 of IRS Pub 527: Residential Rental Property has some examples of how to determine when a property is placed in service.