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 public 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

The date and time calculators answer practical calendar questions: how many days separate two dates, what date follows a chosen interval, or how hours and minutes combine. They can help with rosters, study plans, leave requests, rental periods, project milestones, and travel preparation without counting squares on a calendar by hand.

Enter dates in the order requested and read the labels before accepting a result. A total may include or exclude the starting day, and calendar months do not all contain the same number of days. Leap years add 29 February, so a month-based answer can differ from a fixed number of 24-hour periods.

Civil time uses UTC+12 in standard time and UTC+13 during daylight saving. When an interval crosses the spring jump or autumn repeat, elapsed hours and clock readings may not align in the obvious way. Confirm the location and time zone for appointments, flights, online meetings, and deadlines supplied from overseas.

Working-day calculations need more context than weekends alone. National holidays can be Mondayised, regional anniversary days differ, and an employer or school may use its own closure dates. Check the relevant calendar and official source before using a result for pay, legal notice, enrolment, childcare, or a booking with penalties.

For travel, calculation provides a baseline rather than a live arrival estimate. Add time for school traffic, motorway congestion, road works, weather, parking, transfers, and check-in. Ferries, flights, and regional buses may change after the arithmetic is done, so consult the current operator information before setting out.

Review the input as well as the output. A reversed date, wrong year, or unnoticed time-zone setting can produce a tidy but unsuitable number. Save the dates alongside the result when sharing it, so another person can reproduce the calculation and understand exactly what was counted.

Common questions

Are the start and end dates both included?

Read the result label because inclusive and exclusive counts differ. Retain both input dates when saving or sharing an answer.

Why do months produce different day totals?

Calendar months contain 28, 29, 30, or 31 days. A month-based interval is therefore not interchangeable with a fixed number of 24-hour periods.

How are daylight-saving changes handled?

Calendar dates and elapsed hours can diverge when clocks jump or repeat. Check the device zone and use the calculation type that matches the question.

Does a weekday result include public holidays?

Weekdays alone usually do not account for national, Mondayised, regional, or organisation-specific closures. Verify the calendar and rules that apply.

Can I use the answer for an official deadline?

Use it as a check, then follow the authority's stated counting method. Legal, immigration, payroll, school, and booking rules may define days differently.