Any elective officer whose term of office expires at a time when the total period of his incumbency divided into months results in a fractional month greater than 20 days shall be deemed to have rendered service sufficient to receive credit for a full month provided that such officer contributes to the retirement association prior to the receipt of the first payment of his retirement allowance the contributions required for that month.
Source:
Section 31648.6, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=31648.6..