Time & Date Calculators
Age, date difference & countdown tools. All tools are free, instant, and updated for 2026.
Age Calculator
Find your exact age
Use calculatorDate Difference Calculator
Days between two dates
Use calculatorDays From Today Calculator
What date is X days from now?
Use calculatorBusiness Days Calculator
Count business days between dates
Use calculatorGeneration Calculator
What generation am I?
Use calculatorAbout Time & Date calculators
Date arithmetic looks trivial and is full of conventions. Whether both endpoints count, whether a month means a calendar month or thirty days, whether a deadline in "days" means calendar or business days — each changes the answer, and none is visible in the question.
The other quiet problem is timezones. A date is not a moment in time, and software that treats it as one shifts it by a day for anyone west of Greenwich.
Why date arithmetic is harder than it looks
- Months are not a fixed length
- Adding one month to 31 January has no unambiguous answer, and different systems resolve it differently — some clamp to 28 February, some roll into March. Any tool that adds months is making a choice, and the choice matters for contracts and deadlines.
- Inclusive and exclusive counting differ by one
- The gap between Monday and Friday is four days if you count intervals and five if you count days involved. Neither is wrong; they answer different questions. Most legal and payroll deadlines are inclusive, and most duration calculations are not.
- Business days depend on whose calendar
- Excluding weekends is straightforward. Excluding holidays is not, because the set differs by country, state, industry and employer. A business-day count is only as good as the holiday list behind it.
- Leap years are not simply every four
- Years divisible by 100 are not leap years unless they are also divisible by 400. The rule is why 1900 was not a leap year and 2000 was, and it is the classic source of off-by-one errors in date libraries.
- Time zones move the date, not just the hour
- The same instant is two different calendar dates in two places. Anything that matters — deadlines, ages, filing dates — needs an agreed reference, usually the local date where the obligation applies.
Which one do you need?
- You need the gap between two dates
- Date difference, which gives days, weeks and a years-months-days breakdown.
- You have a deadline in days
- Days from today — and check whether the contract means calendar or business days.
- You are counting working days
- Business days, which excludes weekends and observed federal holidays.
- You need an exact age
- Age calculator, which accounts for leap years.
- You are curious which generation a birth year falls in
- Generation calculator.
Where these go wrong
Assuming adding a month is unambiguous
One month after 31 January has no single correct answer, and systems disagree. For a deadline that matters, work out which convention the obligation actually uses.
Counting days one short, or one long
Inclusive counting includes both endpoints and exclusive counting includes neither. Most legal deadlines are inclusive and most durations are not.
Trusting a business-day count without its holiday list
Weekends are easy; holidays vary by country, state and employer. The count is only as good as the calendar behind it.
Ignoring the time zone on a deadline
The same instant is two different dates in two places. Filing dates and ages need an agreed reference, normally where the obligation applies.
Common questions
Does "within 30 days" include weekends?
Almost always yes. Unless a contract says "business days" or "working days", the count is calendar days including weekends and holidays. Some rules roll a deadline falling on a weekend to the next business day, which helps at the end but does not change the counting.
How many business days are in a year?
About 250. A year has roughly 261 weekdays once the 104 weekend days are removed, and subtracting the eleven federal holidays lands near 250. The exact figure moves by a day or two depending on how the weekends fall.
Why does the day count differ from what I expected?
Usually inclusive versus exclusive counting. Taking 1 to 5 June off is five days of leave, but the difference between those dates is four. Leave and payroll systems count inclusively; date arithmetic subtracts. Add one if you are counting days off.
Does the day count include the start and end date?
Each tool states which convention it uses, because both are legitimate. Duration between two dates normally excludes one endpoint; deadlines expressed in days normally include both. Check which your obligation means before relying on the number.
How is age calculated here?
By completed years since the birth date, which is the ordinary convention in most of the world, with the leap-year rule applied so 29 February birthdays advance correctly. Some legal and insurance contexts use nearest birthday instead, which can differ by a year.
Which holidays are excluded from business days?
Standard federal holidays, with weekends. It cannot know about state holidays, company closures or industry conventions, so for anything contractual check the count against the calendar the agreement actually names.
Why do two date tools give different answers?
Almost always inclusive versus exclusive counting, or a different rule for adding months to a date near the end of one. Both are defensible; they are answering slightly different questions.