(a) For the purpose of recording annual and sick leave on the hourly basis for officers and members of the Firefighting Division of the Fire Department of the District of Columbia, the workday of any workweek shall be considered to be 12 hours.
(b) For the purposes of recording on an hourly basis annual and sick leave taken by officers and members of the Firefighting Division, the following formula shall be used:
(1) During the day shift of 10 hours, one and two-tenths hours of leave shall be charged for each hour taken;
(2) During the night shift of 14 hours, twelve-fourteenths of an hour of leave shall be charged for each hour taken, calculated to the nearest fractional tenth.