The regulations on this are found in subpart D of part 785 of the wage and hour regulations. Time missed or worked within that interval will not be deducted from or added to the time worked, whereas time missed or worked outside that interval will result in that interval being deducted from or added to the time worked. Many employers do not pay employees according to the exact number of hours and minutes they work, but rather utilize some sort of "rounding" or "roundoff" system whereby a certain interval is set that serves as the minimum block of time that will be recognized as a unit of time worked or not worked.
TIME WORK CLOCK PDF
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