Online date and time calculators

Free calculators that work everything out in your browser — choose a tool below.

Age and birthday

Exact age, next birthday, half birthday and star sign — all from one date of birth.

Age calculation Next birthday Half birthday Star sign Chinese sign

Days between two dates

How many days until a date and since a date, working days with bank holidays taken into account, and the full difference between two dates.

Days until a date Days since a date Working days Date difference

Hours and duration

Hours and minutes between two times, and the exact length between two dates.

Hours between two times Duration

Adding and subtracting dates

What date it will be in X days, weeks, months or years — and what date it was X ago.

Add days Subtract days Add weeks Add months Add years

Time zones

Convert the time between cities around the world and plan meetings across several time zones.

Time zone converter Meeting planner

World clock — live clocks

Date arithmetic is easy to describe and irritating to do. Months are different lengths, February moves, weekends interrupt everything, and in the United Kingdom the holidays that knock days out of a working count are not even the same from one nation to the next. The eighteen calculators gathered here exist to take that work off your hands and give an answer you can act on.

The working days calculator is the one that most generic tools get wrong on this side of the Irish Sea. England and Wales, Scotland and Northern Ireland each have their own list of bank holidays, so 2 January is a working day in Manchester and a holiday in Motherwell, and 17 March is an ordinary Tuesday everywhere except Northern Ireland. Counting five working days from a Thursday can therefore land on three different dates depending on which office you are counting for.

What is in the set

Age to the exact day, and the total days lived
Date difference, working days, and days until or since a given date
Adding or subtracting days, weeks, months and years with sensible month-end handling
Hours between two times, including ranges that cross midnight
A time zone converter and a meeting planner covering GMT, BST and the rest of the world

The time zone tools carry a specifically British complication. The UK, the United States and the European Union all observe summer time, but none of them change on the same weekend. Britain moves on the last Sunday in March while America moved a fortnight earlier, so for two weeks in spring the gap between London and New York is four hours rather than five, and a standing call slips out of place without anyone touching the calendar. The converter applies the correct offset for the date you ask about rather than assuming a fixed difference.

Every calculation runs in the browser on your own device. Nothing you type is sent anywhere, stored on a server, or attached to you.

Common questions

Which bank holidays does the working days calculator use?

Whichever list applies to the nation you select, because England and Wales, Scotland and Northern Ireland each observe a different set. A single UK-wide count would be wrong for at least one of them.

Can I get my age in years, months and days rather than just years?

Yes. The age calculator breaks it down to the day and also gives a running total of days lived, which tends to be a larger number than people expect.

Does the hours-between calculator handle a shift that crosses midnight?

Yes. If the finish time is earlier than the start time it treats the finish as falling the next day, so a 10 pm to 6 am shift comes out as eight hours rather than something negative.

What happens when I add a month to 31 January?

You get the last day of February — the 28th, or the 29th in a leap year — rather than a date that does not exist. The same rolling-back rule applies wherever the target month is shorter than the starting one.

Does the time zone converter know about British Summer Time?

Yes, and about the other countries' rules too. It applies the offsets in force on the date you ask about, which matters most in the weeks when the UK and the US have changed their clocks and the other has not.