From the City of Tucson website:
The City of Tucson conducts regularly scheduled partisan elections. These Primary and General Elections are held every odd numbered year.
Upcoming Election Dates
Primary Election - August 25, 2015
General and Special Election - November 3, 2015
How the Mayor and Council are Elected
Council Members are nominated by the ward they wish to represent in the primary election and are elected to the city council at-large in the general election. The Mayor is elected by the voters at-large.
The Mayor and Council Members for Wards 1, 2, and 4 are elected in the same year, while Council Members for Wards 3, 5, and 6 elect their Council Members in the same year.
Elections occur every two years, and the Mayor and Council Members serve four-year terms. There are no term limits for these elected officials.