How did that happen?
We earn vacation time at my job by time served. That is, rather than getting ten or fifteen days at the beginning of the year and parcelling them out, we get X many days per month and accumulate them as we go on. The value of X varies with how long you've been an employee.
Because X is variable, people in odd years of their career gain time in weird fractions, often triple digits after the decimal place. And so it isn't entirely strange that my current vacation day accrual is 8.004 days.
Where did this .004 day come in? It's like a leap-vacation-day. Assuming a standard working day of 7 hours, it's 1.68 minutes.