Time & Date
Time and date calculators solve two different problems: calendar arithmetic (dates, ages and countdowns) and duration arithmetic (hours, timesheets and decimal time). Mixing them up — treating a month as a fixed number of days, for example — is the usual source of errors.
Use the calendar tools when the answer is a date and the timekeeping tools when the answer is an amount of time.
Browse time & date calculators
Calendar & dates
Work & timesheets
Time arithmetic
Which time or date calculator do you need?
Find an exact age in years, months and days, or the difference between two dates.
Add or subtract days, weeks or months from a specific date.
Count down the days until a future date.
Total a weekly timesheet of daily hours and turn it into straight-time pay.
Find the hours and minutes between two times, including a shift that crosses midnight.
Convert hours and minutes into decimal hours for payroll or invoicing.
Count the weekdays between two dates.
Add or subtract durations expressed in hours, minutes and seconds.
Calendar arithmetic versus durations
Calendar units are not fixed: months run from 28 to 31 days and leap years add a day. Adding one month to the 31st of January lands in a different place than adding thirty days, which is why date calculators use calendar rules rather than multiplying by an average month length.
Durations, by contrast, are exact multiples of seconds. Elapsed time is unambiguous, but expressing it in months or years is not — the same 90 days covers three different month spans depending on where it starts.
Timesheets and business days
Timesheet math works in hours and minutes, while payroll often wants decimal hours: divide the minutes by sixty before multiplying by an hourly rate. Small rounding differences over a pay period are normal and depend on the employer's rounding policy.
Business-day counts include Monday to Friday and exclude weekends. Public holidays are not modelled, so subtract them manually if the contract or deadline depends on them.
Conventions that change the answer
- End-date conventions (inclusive or exclusive) and the first day of the week can shift a count by one day.
- Business-day tools count weekdays only — holidays must be removed by hand.
- Payroll rounding (to the minute, the quarter hour or the shift) varies by employer and jurisdiction.