Eligibility for examination for promotion shall be determined as follows:

Patrol officers with one year of probationary experience, in addition to three years experience as a regular patrol officer before the date of the first examination occurrence, shall be eligible for examination for the rank of sergeant; patrol officers with one year of probationary experience in the rank of sergeant before the date of the first examination occurrence, in addition to two years as a regular sergeant, shall be eligible for examination for the rank of lieutenant.