Free Date & Time Tools
The date questions that are annoying to count on your fingers, answered exactly, leap years and all.
Tools in this category
7 tools- Add or Subtract DaysWhat date is 90 days from today? Add or subtract days, weeks, months or years and get the exact date with its weekday.30 May 20261 Mar 2026 plus 90 days
- Age CalculatorExactly how old, in years, months and days, plus what day of the week you were born.Years, months, daysfrom a birth date
- Countdown TimerHow long until it? A live countdown in days, hours, minutes and seconds to any date and time you pick.7d 12h 45mto any date and time
- Date Difference CalculatorHow many days, weeks or working days sit between any two dates.92 days1 Jun to 1 Sep
- Leap Year CheckerIs it a leap year? Instant answer with the reason why, plus the leap years around it.Yes, 366 days2028
- Unix Timestamp ConverterTurn a timestamp into a readable date and time, or a date back into a timestamp.1 Jan 2026 UTC1767225600
- Week Number CalculatorThe ISO week number for any date (including the current week) with the week's Monday-to-Sunday range shown.Week 11 Jan 2026, ISO
The awkward date questions, answered
Adding two numbers is easy. Adding one month to 31 January is not, because the answer depends on which year it is and on what you think a month means. Counting the days between two dates seems trivial until a leap year, a daylight-saving change or a timezone gets involved, and the answer comes out one short.
These tools exist because the obvious implementations are quietly wrong, and because a wrong answer about a date usually looks entirely plausible. Nobody double-checks that they are 36 years and 2 months old.
Why you can trust the number
Counting hours instead of days. The most common bug in date tools is subtracting two timestamps and dividing by 86,400. That works until a clock change makes a day 23 or 25 hours long, and then durations spanning late March or late October come out wrong by one. Every tool here works on calendar dates (plain year, month and day) so the clock never enters into it.
Naive month borrowing. To find the gap between two dates, the obvious approach subtracts the days, and borrows from the months if the result is negative. That fails when the day gap is larger than the borrowed month: 31 January to 1 March produces "one month and minus one days", which is not a duration at all. We use the algorithm the Java date library uses, anchor on the start date plus whole months, then count real days from there, which is correct in every case, including the 29 February ones.
Getting the century leap rule wrong. Most people know about the four-year rule. Fewer implementations handle the exception: centuries are not leap years unless they divide by 400. 1900 had 365 days, 2000 had 366.
Where they get used
Working out an exact age for a form that wants years, months and days rather than just a birthday. Counting notice periods, contract lengths and probation windows. Checking how many working days sit between a deadline and today. Converting a Unix timestamp out of a log file into something a human can read, which is a daily task for anyone who works with servers.
The common thread is that these are quick lookups with a precise answer, where being roughly right is not good enough.
Choices we surface rather than hide
Some date questions genuinely have more than one correct answer, and the honest thing is to let you pick. The clearest example is whether a span includes both end dates: Monday to Friday is four nights or five days depending on what you are counting. Our date difference tool has a switch for it and shows which convention produced the number, instead of choosing silently and leaving you to wonder why it disagrees with your own count.
Similarly, working days are Monday to Friday with no holidays deducted, and the tool says so. Public holidays vary by country and region, and a calculator that quietly applied one country's calendar to everyone would be worse than one that leaves the adjustment to you.
One tool on your home screen
Each date tool here installs on its own rather than as part of a suite. If you look up ISO week numbers every Monday, or count notice periods for a living, put that one calculator on your home screen and it opens straight into the date field, with no menu of other people's tools to walk past first.
What is coming
Adding and subtracting days from a date, ISO week numbers, a working-days calculator with optional holiday lists, time duration arithmetic in hours and minutes, day-of-week lookup, and a leap year checker. Each ships once its edge cases are tested rather than assumed.
Questions people ask
Do these handle leap years correctly?
Yes, including the century rule that catches most implementations out. A year is a leap year if it divides by 4, except centuries, unless they divide by 400, so 2000 was a leap year and 1900 was not. Every date tool here is tested against that and against the awkward 29 February cases.
How is an age of exactly one month calculated?
By the calendar, not by counting 30 days. From 31 January, one month later is 28 or 29 February depending on the year, because there is no 31st. This is the same rule the date libraries in Java and Python use, and it is why 31 January to 1 March comes out as one month and one day rather than a negative number, which is what naive implementations produce.
Do daylight saving changes affect the results?
No, and that is deliberate. These tools work on calendar dates rather than timestamps, so a duration is never one day out because the two dates fell either side of a clock change. Counting hours instead of days is the usual source of that bug.
What counts as a working day?
Monday to Friday. Public holidays are not deducted, because they differ by country, region and sometimes by employer. If you need holidays excluded, subtract them yourself, the tool gives you the weekday count to start from.
Should a duration include both end dates?
It depends what you are counting, which is why the date difference tool lets you choose. From Monday to Friday is four days if you are counting nights in a hotel, and five if you are counting days worked. Neither is wrong; picking silently for you would be.
Do these cost anything?
No, and they never will. Every date tool here is free to use as often as you like, with no account to make, no daily limit and no paid tier keeping a feature back.