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About Hours
Hours and minutes between a start and an end date and time.
Federal law sets the floor for overtime and record-keeping, but state rules can be stricter and a handful of states require daily overtime past eight hours. Salaried employees are exempt only when their duties and pay meet the Department of Labor tests.
American payroll law sets a 40-hour week, requires 1.5 times the regular rate beyond it for non-exempt employees, and does not require paid breaks or a lunch. Employers may round punch times, and an unpaid meal break is the commonest reason a time card totals less than the hours spent at work.
Hours worked, hours paid and hours scheduled are three different numbers, and the gap is usually unpaid meal breaks, rounding and travel time. Overtime is counted weekly under federal law, though several states impose daily thresholds.
A 30-minute unpaid lunch, five days a week, is two and a half hours — about 6% of a 40-hour week that never reaches the paycheque.
Record-keeping is the obligation behind the arithmetic: employers must keep accurate hours for non-exempt staff, and rounding practices must not systematically shave time. Averaging across a pay period cannot be used to avoid overtime earned within a given week.
Hours Calculator sits with the rest of the library's everyday work, and it rests on the same timekeeping arithmetic the way a manufacturer's label or a timetable does. Its answer is only as good as the assumptions standing behind it.
The quantities it works from — start date, start time, end date, end time and break — are the ones a real timekeeping question actually turns on, and each carries a convention of its own, set out below.
Everyday arithmetic in the United States carries conventions that are easy to miss: dates run month before day, distances and weights follow customary units, and prices are quoted before tax. Those conventions make a surprising share of daily sums come out differently from the same question asked elsewhere.
The figures in this section follow American practice unless the subject itself is international.