The probationary period for an assistant professor starting their career without credit for prior professorial experience is seven academic years. The "tenure clock" is the commonly used metaphor for the imaginary meter that counts down this probationary period. Credit for prior professorial experience, discussed in the “Years of Credit toward Tenure,” section, can be thought of as starting the clock earlier (e.g., 1, 2, or 3 years earlier than the faculty member’s start date as tenure-track faculty at CU Boulder), and therefore placing the mandatory tenure review date in the 7th year of the tenure clock. At the end of the probationary period, a decision on whether to promote and tenure is required according to Regent Law. A negative decision results in issuance of a one-year terminal appointment. The purpose of this terminal year is to provide the faculty member ample opportunity to explore other career options, and to allow a transition period for the primary unit to adjust for the impending departure of the faculty member. 

There are occasions when the tenure clock is adjusted. This is generally referred to as "stopping the clock;" extending the clock also happens on rare occasions. Leaves associated with extended illnesses, accompanied by sick leave, parental leaves associated with childbirth, and family leaves are the most common reasons for stopping the clock. Stopping the clock because of a leave does not prejudice the tenure and promotion review in any way.
A copy of the campus policy Adjustments to The Tenure Clock

Faculty members are urged to consult their department or division chair in all matters related to reappointment, tenure, and promotion. In addition, the Associate Vice Chancellor for Faculty Affairs (AVCFA) is available to faculty members needing assistance or explanation. The AVCFA can recommend workshops and mentors for faculty members seeking assistance in dossier preparation, building a teaching portfolio, and other matters related to the review and evaluation process.