Fair Rental Price & Days Rented - Property Had Squatters

If squatters suddenly appeared in my rental house and I couldn't get rid of them, how does that affect the "fair rental price" and the days rented? My house was occupied for more than half the year by people who paid me nothing and with whom I had no contractual relationship, and which the police and courts took forever to get out of there. I couldn't rent it to anyone else.

 

And what about a tenant who had a lease for a fair rental price but stopped paying? Do I count the days rented as through when the tenant last paid, or when they actually moved out?