Section 4b. Requests for vacation over the Thanksgiving holiday/weekend must be submitted, in writing, between September 1 and 15. The Employer will respond to these requests, in writing, by September 23. If a conflict should arise between requests made between September 1 and 15, seniority shall prevail within the nursing unit and on the shift. Shifts are defined as day, evening, and night. Shifts will be determined by the majority of hours on one (1) of these shifts, however, if an employee works an equal number of hours on two (2) shifts, the employee's shift will be the starting shift. Requests submitted after September 15 shall be handled on a first-come, first-serve basis.