timeclock-get-workday-function

timeclock-get-workday-function is a variable defined in `timeclock.el'.
Its value is

nil

• This variable may be risky if used as a file-local variable.

Documentation:
A function used to determine the length of today's workday.
The first time that a user clocks in each day, this function will be
called to determine what is the length of the current workday. If
the return value is nil, or equal to `timeclock-workday', nothing special
will be done. If it is a quantity different from `timeclock-workday',
however, a record will be output to the timelog file to note the fact that
that day has a length that is different from the norm.

You can customize this variable.