It can be somewhat confusing as to when the 30 days starts running. It would be logical if the 30 days started from the time it was mailed or the time it was received. However, it's a little more confusing than that.
The 30 days start at the beginning of the next billing cycle. So if rent is due on the 1st of the month then the tenants will have until the end of the month to stay in the property. For example, if a landlord sends the 30 day notice on the 5th of August. The tenants can stay until September 30th! Make sure you factor this unusual system of counting into your plans. Lastly, make sure the 30 day notice is sent via certified mail!
Furthermore, a tenant who does not vacate by the end of the 30 days may be liable to the landlord for additional damages. A.R.S. § 33-1375(C) states:
"If the tenant remains in possession [of the property] without the landlord's consent after expiration of the term of the rental agreement or its termination, the landlord may bring an action for possession and if the tenant's holdover is willful and not in good faith the landlord, in addition, may recover an amount equal to not more than two months' periodic rent or twice the actual damages sustained by the landlord, whichever is greater."
So Arizona tenants who do not leave by the end of the 30th day face the risk of having additional fees added onto the judgment obtained by the landlord. If you need help from an Arizona real estate attorney then contact Clint Dunaway at firstname.lastname@example.org or 480-389-6529.