Date & Time
Ages, date math, timers and time zones. These tools are free, need no account, and come with simple step-by-step instructions.
- Age CalculatorExact age in years, months and days, plus your next birthday.
- Days Between DatesDays, weeks and months between two dates.
- Add or Subtract DaysWhat date is 30, 60 or 90 days from a date?
- Day of the Week FinderWhat day of the week was (or will be) any date?
- Business Days CalculatorWorking days (Mon–Fri) between two dates.
- Week Number CalculatorISO week number for any date.
- Countdown TimerA simple timer with an alarm sound when it ends.
- Online StopwatchStart, stop, lap and reset, accurate to the hundredth.
- Pomodoro Focus Timer25-minute focus sessions with short and long breaks.
- Hours & Minutes CalculatorAdd or subtract durations written as signed hours:minutes.
- Recurring Date GeneratorGenerate a bounded list of dates separated by a fixed day interval.
- Next Birthday CountdownFind the next occurrence of a month and day from a reference date.
- Leap Year Checker & Calendar ExplanationCheck whether any year is a leap year using Gregorian calendar rules.
- Habit Streak & Milestone Day CounterCount total days, weeks, and milestones elapsed since a significant date.
- Flight Duration & Time Zone Delta CalculatorCalculate true in-flight elapsed duration across international time zones.
- Daylight Duration by Latitude CalculatorEstimate total daylight hours by geographic latitude and month.
- Asphalt Heat & Dog Walking Safety CalculatorEstimate asphalt ground temperature from air temperature for paw safety.
- Golf Handicap Differential Score CalculatorCalculate your single-round handicap score differential.
- Subwoofer Enclosure Volume CalculatorCalculate internal cubic feet and liters for speaker box builds.
- Water Heater Tank Capacity Sizing CalculatorEstimate water heater gallon capacity and first-hour rating needed.