Vacation Accrual Usage

Balance

I am an exempt employee. My company permits us to take vacation in 4
hour allotments.  Requests for vacation are made in advance and
approved.  Payroll is done every two weeks. Our week starts on a Monday
and ends on Sunday for payroll purposes. All employees, even those of us
who are exempt must clock in and out.  

On a given week, I
requested and was approved for 8 hours of vacation.  As it worked out,
do to my workload, I actually worked 40 hours in four days.  The HR
person is telling me that although I worked 40 hours, I still need to
take my 8 hours of vacation in order to take this Friday off.  I have
been classified as an exempt employee for the past 25 years.  No other
employer has ever asked me to take accrued vacation when I have already
worked 40 hours in a given workweek.  BTW, I worked 40 hours the week
before, so I am not short hours in the pay period. 

Is this
legal?   The HR person is telling me that all exempt employees are
expected to work more than 40 hours a week.  Typically I work 42-44
hours each week, because the work never ends.  Can a company require me
to take vacation even when I have fulfilled my 40 hour requirement?

Thanks in advance for your reply.

HRforME

I answered on the other post.