31. One year of service or part of a year of service is credited, for each calendar year, to the employee for the service accumulated if the contributions have been paid and not refunded and for service that is otherwise credited to the employee under the provisions of the plan. The same applies with respect to an employee who has at least 35 years of credited service without being required to pay contributions.
Service is credited according to the number of days and parts of a day for which the employee paid or was exempt from contributions and the days and parts of a day otherwise credited to the employee out of the number of contributory days in a year, that is, 200 or 260, according to the basis of remuneration. If, in the total number of days and parts of a day, there remains part of a day that is less than 0.5, the fraction is disregarded or, if the fraction is equal to or greater than 0.5, it is considered a full day.