Gov. Code, § 18901

(a) The department may remove all names from open and promotional eligible lists after they have remained thereon for more than one year from the date of the adoption of the lists that created their eligibility, and shall remove all names from lists of eligibles not later than four years after the adoption of the lists that created their eligibility.

Whenever an open or a promotional eligible list has fewer than three names of persons who are willing to accept employment, all names on the list may be removed even though one year has not elapsed from the date of the adoption of the list.

(b) When a list of eligibles becomes exhausted for temporary or permanent employment before the legal expiration of the list, and a new list of eligibles for the same class is created by examination to supply the demands of the service, such new list shall become a part of the list of eligibles to be certified to the positions covered by the list. Those holding places on the prior list shall be given preference for appointment until such time as the prior list may automatically expire or all names are removed therefrom by action of the department. When the prior list has expired by reason of limitation of time, or the names have been removed therefrom by order of the department, then certification shall be made solely from the latter list.

(c) The department or a designated appointing power shall include in the announcement of any examination that the list of eligibles secured thereby will expire not less than one but less than four years after the adoption of such list.

(d) The department or a designated appointing power may make changes in its records to correct clerical errors both before and after the announcement of an eligible list; provided, that any changes of rank, or addition or subtraction of names, made on lists of eligibles because of clerical errors or reratings, shall not change the date of the adoption of such lists, nor give to any persons the right to claim beginning date of eligibility other than the date of the adoption of the original eligible list that created their eligibility.