6-in-1 Age, Date & Time Calculator
Exact age in years, months and days; the gap between two dates; a date shifted forward or backward; elapsed time down to the second; the weekday of any date; and a leap-year check.
Calendar maths, not legal proof. Results follow the Gregorian calendar and the dates you enter. For official age or deadline proof, rely on your documents or the issuing authority's rules.
6-in-1 Age, Date & Time Calculator
Pick a mode below — each one solves a different calendar question.
What you can calculate
Six calendar questions, answered from real Gregorian days.
Exact age
Years, months, days — plus totals in smaller units.
Date difference
Gap between two dates, end day optional.
Add / subtract
Shift a date by days, weeks, months or years.
Time duration
Elapsed days, hours, minutes and seconds.
Day of week
Weekday and day-of-year for any date.
Leap year
Rule check plus the next leap year.
Your result
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Gregorian calendar maths on the dates you enter — no time zones, no business-day or holiday exclusions. Age and date-gap modes count calendar days, not times of day.
How each mode works & worked examples
The rule behind every mode, a verified example, and the situations each one is meant for.
Exact age
Years, months and days as of any reference date.
Use case
A form asks for age in years, months and days, or a parent wants a child's exact age for a school or vaccine schedule.
Formula & example
Born 15 Jun 1996, as of 12 Oct 2026 → 30y 3m 27d (11,076 days)
Assumption: calendar days only — birth time of day is not used.
Who uses it
- Form fillers
- Parents
- HR and admissions teams
Applications
Eligibility checks, birthday countdowns, service-length records.
Difference between two dates
The gap, with the end day counted only if you ask.
Use case
A renter wants the exact length of a lease, or a student wants the days left until an exam, counted the way their institution counts them.
Formula & example
1 Jan 2026 → 31 Jan 2026, included → 31 days (4 weeks, 3 days)
Assumption: both dates are local calendar days at midnight.
Who uses it
- Project managers
- Renters and landlords
- Event planners
Applications
Deadlines, lease periods, campaign lengths, countdowns.
Add or subtract from a date
Shift any date by days, weeks, months or years.
Use case
A buyer wants the exact date a 90-day warranty ends, or a planner needs the date 6 months before an event.
Formula & example
1 Jan 2026 + 90 days → 1 Apr 2026 (Wednesday)
Assumption: month/year shifts follow calendar rules (31 Jan + 1 month → 28/29 Feb).
Who uses it
- Shoppers tracking warranties
- Legal and compliance teams
- Travel planners
Applications
Return windows, due dates, notice periods, visa validity.
Time duration, to the second
Elapsed time between two exact timestamps.
Use case
An hourly worker clocks 09:00 to 17:30 and wants the exact worked time for a timesheet, not a rounded guess.
Formula & example
09:00:00 → 17:30:00 same day → 0d 8h 30m 0s (8.50 hours)
Assumption: both timestamps are read exactly as entered, no time-zone conversion.
Who uses it
- Hourly workers
- Freelancers billing time
- Event and race organisers
Applications
Timesheets, invoicing, meeting lengths, race splits.
Day of the week
Weekday and day-of-year for any date.
Use case
Someone booking a venue for 25 Dec next year wants to confirm the weekday before confirming with guests.
Formula & example
25 Dec 2026 → Friday, day 359 of 365
Assumption: proleptic Gregorian calendar for all supported years.
Who uses it
- Event planners
- Genealogists
- Students of history
Applications
Bookings, anniversary planning, historical date checks.
Leap year check
The 4 / 100 / 400 rule, plus the next leap year.
Use case
Someone born on 29 Feb, or planning a leap-day event, wants to know which years actually contain that date.
Formula & example
2026 → not a leap year; next one is 2028
Century example: 1900 no, 2000 yes.
Who uses it
- Leap-day birthdays
- Developers testing date code
- Teachers and trivia hosts
Applications
Event planning, software date-handling tests, calendar education.
What this calculator includes — and what it leaves out
Plain Gregorian arithmetic with stated assumptions; no hidden rules.
Tool limits
- Gregorian calendar only — no Hijri, lunar or fiscal calendars
- No time-zone conversion — times are read exactly as entered
- Age and date-gap modes use calendar days, not times of day
- Works on desktop, tablet, and mobile with no install
What this tool does
- Computes exact age with a next-birthday countdown
- Counts date gaps with or without the end day
- Shifts dates by days, weeks, months or years with calendar-correct month ends
- Measures durations to the second and checks leap years
What this tool does NOT do
- It doesn't exclude weekends, public holidays or business days
- It isn't a legal record of age or a deadline authority
- Calculations run in your browser; the tool does not save your dates
- It doesn't handle DST shifts — duration uses the clock times you type
References worth bookmarking
Where the calendar rules come from, plus related tools on this site.
Official & useful links
Questions people ask about dates
Straight answers on how each mode counts, and what it deliberately ignores.
Using the modes
What can I calculate with this tool?
Six things: your exact age from a date of birth, the difference between two dates, a new date after adding or subtracting days/weeks/months/years, the duration between two date-and-time points down to the second, the day of the week for any date, and whether a given year is a leap year.
How does the age calculation handle leap years?
It works from actual calendar days using the Gregorian calendar, so February 29 in a leap year is counted correctly without any separate adjustment.
What's the difference between "Date Difference" and "Add/Subtract Date"?
Date Difference takes two dates you already have and tells you the gap between them. Add/Subtract Date takes one date and a number of days, weeks, months or years, and tells you the resulting date.
Does "include end date" change the result?
Yes. With it checked, both the start and end day are counted (so Jan 1 to Jan 3 is 3 days). Unchecked, only full days between the two dates are counted (so Jan 1 to Jan 3 is 2 days).
Precision & privacy
How precise is the Time Duration calculator?
It calculates down to the second using the exact date and time you enter for the start and end points, then breaks the total down into days, hours, minutes and seconds.
Can I find out what day of the week a date falls on?
Yes. The Day of the Week tool takes any date, past or future, and tells you whether it falls on a Monday, Tuesday, and so on.
How do I check if a year is a leap year?
Enter the year in the Leap Year tool. It applies the standard rule — divisible by 4, except century years, which must be divisible by 400 — and also shows the next leap year.
Is my data stored anywhere?
No. Every calculation runs locally in your browser. The dates and times you enter are never sent to or stored on a server.
Six calendar answers, one free tool
No signup required. Age, gaps, shifts, durations, weekdays and leap years — computed from real Gregorian days in your browser.