Annually, though the review process just changed to have everyone on the same review cycle so it's been 1.5 years - but will go back to yearly again.
If one is lucky not to be threatened with verbals or write ups while trying to do their best, they occur annually...
Used to be yearly
Answered - Anonymous (Current Employee) - Glen Allen, VA
Annually towards the end of the year; separate from quarter raises if tiers are completed
Answered - Administrator II (Current Employee) - City of Sunrise, FL
Once a year
Answered - Employee (Current Employee) - Raleigh, NC