calc / date & time / TIME
Time Calculator
Duration arithmetic without carrying sixties in your head — two times in, one normalised answer out, with totals in every unit.
A ± B days · hours · minutes · seconds
§1Why time maths trips people
The classic error is decimal-adding clock values — treating 2:45 as 2.45. Two hours forty-five minutes is 2.75 hours, and the gap between those two readings compounds fast across a timesheet.
Adding the columns naively gives “3h 83m 75s” — right, but useless until you carry the sixties. Going through seconds makes the carry automatic.
§2The gotchas
Minutes are sixtieths. To convert: minutes ÷ 60. So 2h 45m = 2.75h, and 7.5 hours is 7h 30m, not 7h 50m. Payroll systems want the decimal form; humans write the colon form.
This page adds durations. “3:30 PM plus 2 hours” is a clock question — different because of midnight wrap and time zones. For that, use the hours calculator or time zone calculator.