Calculate ages, durations, time zones, countdowns, and life stats.
Calculate your exact age in years, months, weeks, days, hours, and minutes.
Calculate the exact days, weeks, months, or years between any two dates.
Calculate business days between two dates, excluding weekends and US federal holidays.
Find out what day of the week any date falls on, past, present, or future.
Add or subtract hours, minutes, and seconds. Calculate duration between two times.
Convert times between any two time zones instantly with DST status and business hours.
Live times for 60+ cities with DST badges and a built-in meeting planner.
Find how many days until any event, holiday, birthday, or deadline.
Visualize your entire life as a grid of weeks. See how much you have lived and what remains.
Enter your birthdate and watch your life stats unfold, heartbeats, breaths, and steps, ticking live.
Watch humanity grow in real time with live birth and death counters and regional breakdowns.
How many Mondays do you have left until retirement? Based on the 4,000 Weeks concept.
Create a live countdown timer to any date and time. Share countdowns for events and milestones.
How old are you on every planet? Enter your birthday for your age across the solar system.
Current moon phase, moonrise/set times, illumination, and full moon calendar. Pure astronomical math.
See which planets are visible tonight with rise and set times, brightness, and SVG diagrams.
Exact sunrise, sunset, golden hour, and solar noon for any location. No API, works offline.
Date arithmetic looks simple and almost never is. Months have four different lengths, leap years follow a rule with an exception inside it, business days skip weekends and holidays, and time zones shift twice a year on dates that do not match between countries. Our free date and time calculators handle all of it, from working out an exact age to counting business days to a contract deadline to checking what time it is on the other side of the world right now.
This category also holds a set of tools that are less about scheduling and more about perspective. The Life Calendar renders a human lifespan as a grid of weeks. Your Life in Numbers converts the years you have lived into heartbeats, breaths, and hours slept. The Mondays Left Calculator answers a question most people have never asked and do not forget the answer to. They use the same date math as the practical tools, applied to a different question.
| What You Are Doing | Best Calculator | What You Get |
|---|---|---|
| Working out an exact age | Age Calculator | Years, months, days |
| Counting to a contract or project deadline | Business Days Calculator | Weekdays only |
| Days between two dates | Date Difference Calculator | Total days elapsed |
| Tracking time to an event | Days Until Calculator, Countdown Calculator | Live countdown |
| Scheduling across time zones | World Clock | Local times worldwide |
| Adding or subtracting hours | Time Calculator | Hours and minutes |
| Putting a lifespan in perspective | Life Calendar, Your Life in Numbers | Weeks, days, heartbeats |
| Planning around daylight | Sunrise and Sunset Calculator | Golden hour, daylight length |
The common shortcut is to divide the number of days by 365.25 and call the result years. It is close, and it is wrong in ways that show up at exactly the wrong moment. Month lengths vary from 28 to 31 days, so adding one month to 31 January has no obvious answer. Leap days mean the gap between two birthdays is sometimes 365 days and sometimes 366. Someone born on 29 February has a legal birthday that differs by jurisdiction in non leap years.
Calculating properly means walking the calendar rather than doing division. That is what these tools do. It is also why the answer they give matches what a government form, a payroll system, or a court filing would produce, which a rough estimate often does not.
Scheduling a call between two countries is not a matter of memorising an offset, because the offset moves. Regions that observe daylight saving shift on different dates, so the gap between two cities can change twice a year and be temporarily unusual for a few weeks in between. Some places never shift at all, and a handful sit on half hour or quarter hour offsets rather than whole hours. Checking the current local time directly removes the guesswork, which is what the World Clock is for.
Age is counted in completed years, then completed months, then remaining days, which is why a simple subtraction of dates gives the wrong answer. Someone born on the 31st of a month has no exact anniversary in months with 30 days, and someone born on 29 February only has a true birthday every fourth year. Our age calculator walks the calendar forward month by month rather than dividing total days by 365.25, so the result matches how age is recorded on official documents.
A year is a leap year if it divides evenly by 4, except century years, which must also divide evenly by 400. That means 1900 was not a leap year but 2000 was. The rule exists because Earth's orbit takes about 365.2422 days rather than a neat 365.25, so adding a day every four years slightly overcorrects and the century exception pulls it back. Any date calculation spanning more than a year needs this rule applied correctly or it drifts.
Calendar days count every day including weekends and holidays. Business days count only Monday through Friday and typically exclude public holidays. The distinction matters in contracts, shipping estimates, court filings, and payment terms, where a 30 day window can mean six weeks of real time if it is measured in business days. Always check which basis a deadline uses before you assume you have a month.
Roughly 10,957 days, allowing for seven or eight leap days depending on the exact birth date. That works out to about 262,968 hours. Numbers like these are why the Life Calendar and Your Life in Numbers tools exist: a lifespan expressed in years feels abstract, while the same span in weeks or days tends to land differently. A 30 year old with an average life expectancy has already spent close to 40 percent of it.
Daylight saving transitions rarely line up between countries. The United States and the European Union both shift their clocks but on different dates, so for a few weeks each year the usual offset between, say, New York and London is one hour different from normal. Several regions do not observe daylight saving at all, and some are offset by 30 or 45 minutes rather than a whole hour. Checking a live world clock beats doing the arithmetic from memory.
The synodic month, meaning one full cycle from new moon to new moon, averages about 29.53 days. That is why moon phases drift relative to calendar months and why some calendar months contain two full moons. The moon phase calculator tracks the actual cycle rather than approximating it at 30 days, which matters for anyone planning around night visibility, tides, or photography.