When exactly is the start of rental?

On August 1st we decided to convert our apartment from personal use to a rental, however we wanted to remodel it first in order to find a decent tenant and collect more money. By August 31st we removed all our personal stuff from the apartment. The big remodeling started on September 1st  and finished on November 30th. We started advertizing the apartment on December 1st and found a tenant on December 15th when we also collected the first rent.

When exacly is the date I can start deducting apartment expenses (like the HOA) and start the apartment depreciation?