Time arithmetic without ambiguity

Calculate days, hours and work time.

Pick the calculation you need. Every result explains what was counted, what was excluded and which assumptions were used.

Calculate hours Days between dates

Calculators

Start with the question you have

Hours & time

Clock arithmetic, durations, shifts and conversions.

Hours and Minutes CalculatorAdd or subtract hour-and-minute durations.Time CalculatorAdd or subtract time from a clock value.Time Duration CalculatorCalculate elapsed time between two clock times.Decimal Hours CalculatorConvert between clock-style time and decimal hours.Minutes to Decimal HoursTurn minutes into a decimal-hour value.Hours to Minutes CalculatorConvert decimal hours into minutes.Add Hours to a TimeAdd hours and minutes to a clock time.Subtract Hours from a TimeSubtract a duration from a clock time.

Work time

Single shifts and weekly time cards.

Shift Hours CalculatorCalculate shift hours after subtracting breaks.Time Card CalculatorAdd daily shifts into a weekly hours total.

Dates & days

Date differences, date arithmetic, weekdays and relative dates.

Days Between Dates CalculatorCount days between two dates without DST errors.Date CalculatorFind a date a set number of days before or after another date.Business Days CalculatorCount Monday–Friday days between dates.Days From Today CalculatorCalculate a future date from today.Days Ago CalculatorCalculate a past date from today.Days Until CalculatorCalculate days from today until a future date.Days Since CalculatorCalculate days elapsed since a past date.Workday CalculatorAdd or subtract working days, excluding weekends and custom holidays.

Live tools

Real-time timing tools that run in your browser while the page stays open.

StopwatchTime anything with start, pause, resume and laps.Countdown TimerCount down from a set duration with an end-of-time alert.Online Alarm ClockSet an alarm for a specific clock time, right in your browser.

Time zones

Compare current time across cities, or convert a specific date and time between zones.

World ClockCheck the current time in multiple time zones at once.Time Zone ConverterConvert a specific time from one time zone to another.

Clinical research

Protocol-style visit scheduling for clinical research coordinators.

Clinical Trial Visit Window CalculatorGenerate a multi-visit schedule with asymmetric early/late windows.

Built for trust

Small details matter in date and time calculations.

Clear counting. Inclusive and exclusive date counts are labeled instead of hidden.

Overnight-aware. Time durations can cross midnight without producing a negative surprise.

No account required. The calculations run in your browser and require no login.