An employee on an approved leave of absence shall continue to accumulate seniority during the period of his absence. An employee on an approved leave of absence of thirty (30) calendar days in any calendar year or less shall have his hospitalization and surgical insurance and group insurance death benefit continue in force by the City. An employee on an approved leave of absence for more than thirty (30) calendar days in any calendar year shall not receive fringe benefits during the period of such leave, however, an employee may arrange to prepay through the Division of Accounts the premiums necessary to continue the employee's hospitalization and surgical insurance and group insurance death benefit in force during the period of time the employee is on leave.