Date and Time Calculators
Date and time calculators for counting days, adding hours, converting time zones and reading other calendars.
Dates and ages
- Date CalculatorDays between two dates, or a date shifted by any interval. The date calculator answers in years, months and days as well as a plain day count.
- Age CalculatorThe age calculator gives your exact age in years, months and days, the next birthday, the weekday you were born, and your age on any date.
- How Many Days in a MonthHow many days in a month, for any month and year, with the weekdays and weekend days counted and the weekdays that occur five times named.
- Dog Age CalculatorThis dog age calculator turns dog years into human years two ways: the chart the AVMA publishes for pet owners, and the 2020 DNA methylation study of Labrador retrievers. They disagree most in the early years.
- Cat Age CalculatorThis cat age calculator converts cat years to human years by the table in the AAFP-AAHA Feline Life Stage Guidelines: 15 for the first year, 24 at two, then 4 for each year after. It is a way of picturing a cat's age, not a measurement.
Clock time
- Time CalculatorAdd or subtract two lengths of time and the time calculator carries 60 seconds into a minute, 60 minutes into an hour and 24 hours into a day.
- Time ConverterA time converter for seconds through years, and for decimal hours to hours and minutes: 7.25 hours is 7:15, not 7:25.
- Time Zone ConverterThe time zone converter turns a time in one zone into another, with the offset, the date carry, and whether daylight saving moves the gap during the year.
- Daylight Saving Time CalculatorDaylight saving time dates for any year in the US, Europe, Australia and New Zealand, with the day the clocks go forward, the day they go back, and the rule behind both.
- Military Time ConverterThe military time converter turns 3:45 PM into 1545 and 1545 into 3:45 PM, with how the time is said aloud and the full hour-by-hour table.
- Unix Timestamp ConverterThe Unix timestamp converter turns epoch time in seconds, milliseconds, microseconds or nanoseconds into a date in UTC and any time zone, and a date back into a timestamp. The unit is read from the size of the number.
Calendars
- Hebrew Calendar ConverterThe Hebrew calendar converter computes each date from the fixed arithmetic calendar (the molad, the postponement rules and the 19-year cycle) rather than looking it up, so any year comes out right.
- Julian Date ConverterTwo different things are both called a Julian date. This Julian date converter gives both, the day-of-year code and the astronomical Julian Day, and says which one you probably mean.
- Moon Phase TodayThe moon phase today, with how much of the disk is lit, the moon's age and the next new and full moon.
More categories
- Math CalculatorsMath calculators that show their work: arithmetic, algebra, statistics, and a calculus calculator for derivatives and integrals, with exact answers in fractions and radicals where they exist.
- Geometry CalculatorsGeometry calculators for shapes, lines and angles, with the formula behind each answer explained.
- Chemistry Calculators, Physics and Lab ToolsChemistry calculators, physics calculators and molecular biology tools for the bench and the problem set.
- Conversion CalculatorsConversion calculators for unit conversion, number bases, Roman numerals and angles. The unit converter shows the factor it used and a conversion chart for the values around yours.
- Business CalculatorsBusiness calculators for pricing a product and for the unit economics behind a company: margin, markup, break-even, ROI, CAC, LTV and churn.
- Random GeneratorsRandom generators that draw fairly, from your browser's cryptographic generator: numbers, names, teams, coin flips and dice.
- Everyday Cost CalculatorsCost calculators for what a meal, a drive or an appliance actually costs: tips, split bills, fuel, electricity and EV charging.
- Free Online ToolsFree online tools for codes and text, run in your browser with nothing uploaded.