About Date & Time
Dates are where mental arithmetic fails most reliably. Months have different lengths, February changes size every four years, and time is base 60 rather than base 10 — which is why subtracting 09:45 from 17:30 in your head so often produces a number that is quietly wrong by fifteen minutes.
These tools use real calendar arithmetic rather than approximations. Age is counted in whole years, then whole months, then days, the way a passport office or a school registration form counts it — not by dividing days by 30. Leap days are included wherever they fall. Shifts that run past midnight are recognised as overnight rather than treated as negative time.
For deadlines expressed in business days, the working days calculator lets you set which weekdays count and paste in your own public holidays, because holiday calendars differ by country, region and sometimes employer. For timesheets, the work hours calculator totals a full week and converts it to the decimal hours payroll systems expect.