(a) As used in section 7(k), the term ``work period'' refers to any
established and regularly recurring period of work which, under the
terms of the Act and legislative history, cannot be less than 7
consecutive days nor more than 28 consecutive days. Except for this
limitation, the work period can be of any length, and it need not
coincide with the duty cycle or pay period or with a particular day of
the week or hour of the day. Once the beginning and ending time of an
employee's work period is established, however, it remains fixed
regardless of how many hours are worked within the period. The beginning
and ending of the work period may be changed, provided that the change
is intended to be permanent and is not designed to evade the overtime
compensation requirements of the Act.
(b) An employer may have one work period applicable to all
employees, or different work periods for different employees or groups
of employees.