Term Dates Calculator

Term Dates Calculator: calculate term dates for students and teachers. Clear steps and worked examples.

An age calculator works out your exact age from your date of birth — not just a rounded year count, but the precise number of years, months, and days that have elapsed. Enter your date of birth and any reference date (today, a future birthday, or a past event) and the result shows the composite breakdown alongside the total in calendar days, working days, and weeks. The calculator also shows how many days until your next birthday. Length Conversion Calculator and Weight Conversion Calculator are useful companions for date arithmetic and planning around personal milestones.

Age arithmetic is more nuanced than dividing days by 365. Calendar months have different lengths (28–31 days), leap years add a day every four years, and a birthday that falls on 29 February only recurs every four years. The correct approach counts complete birthday anniversaries from birth to reference date, then counts remaining whole months and remaining days — giving the human-readable "X years, Y months, Z days" result that matches what a doctor, insurer, or admissions office would calculate.

Enter your date of birth in the first field. Any date in the past is valid.
Set Age on date to the date you want to measure from — it defaults to today, but you can set it to a past or future date to answer "how old was / will X be on…" questions.
The top result shows your exact composite age: years, months, and days — calendar-aware, not an approximation.
The next birthday countdown shows how many days remain until your next birthday and what age you will turn.
The Full breakdown section shows the same span expressed as total calendar days, working days (Mon–Fri), complete weeks, and a decimal year figure.
Use the Bonus: date math section at the bottom to add or subtract any number of days from any date — useful for calculating deadlines, notice periods, or delivery windows.

How exact age is calculated

Composite age (years / months / days): subtract the day-of-month components, borrowing from the months column if the result goes negative; then subtract the month components, borrowing from the years column if needed. This produces whole-number years, months (0–11), and days (0–30) that match the human convention for stating age.

Why not just divide by 365.25? Dividing elapsed days by 365.25 gives a decimal year (e.g. 14.75 years) but not the years/months/days breakdown. It also slightly misaligns with birthdays — someone born on 1 January is not "14 years old" until their 14th birthday, regardless of the day-count fraction.

Leap year rule: a year is a leap year if divisible by 4, except century years, unless also divisible by 400. So 2000 was a leap year; 1900 was not; 2100 will not be. People born on 29 February turn a year older on 28 February (or 1 March, depending on jurisdiction) in non-leap years — this calculator uses 28 February consistently.

Calendar days between two dates: (Reference date − Birth date) in milliseconds ÷ 86,400,000. Handles all month-length and leap-year variations automatically.

Understanding the age calculator results

Composite age vs. decimal age

The composite age (e.g. "14 years, 9 months, 0 days") is the human-readable format used in medical records, legal documents, passport applications, and insurance forms — it counts complete anniversaries, not fractions. The decimal age in the full breakdown (e.g. "14.75 years") is used in research and statistical contexts where a continuous numeric value is needed. The two will rarely match exactly because months have different lengths; both are correct for their respective purposes. Working days counts Monday–Friday only and excludes weekends, but does not subtract public holidays — subtract those manually if needed for legal or contractual deadlines.

Education tips and best practices

Set "Age on date" to a future date to find out how old someone will be at a future event — useful for school admissions (age on 1 September) or retirement planning.
Set "Age on date" to a past date to answer retrospective questions — "how old was X when Y happened?"
For school year eligibility (England): children must start school in the September after their 4th birthday. Enter the child's date of birth and set "Age on date" to 1 September of the relevant year.
For insurance and medical forms, age is almost always the composite years figure — not the decimal — as of the relevant reference date.
Leap-year birthdays (29 February): in non-leap years, this calculator treats the birthday as 28 February for the next-birthday countdown. Some jurisdictions use 1 March — check the specific rule if it matters for legal purposes.
Verify calculated dates near month-end carefully — month arithmetic edge cases (born on the 29th, 30th, or 31st) can produce small rounding differences near month boundaries.
Use ISO 8601 date format (YYYY-MM-DD) in written communications to avoid ambiguity between DD/MM/YYYY (UK) and MM/DD/YYYY (US) conventions.

A standard Gregorian year has 365 days; the average Gregorian year is exactly 365.2425 days when accounting for leap year rules.
There are on average 252 working days per year in the US (365 − 104 weekend days − 9 federal public holidays observed on weekdays).
A person born on 29 February (leap day) has an actual birthday only every 4 years — legally and practically they are treated as born on 28 February or 1 March in non-leap years depending on jurisdiction.
The longest possible month is 31 days; the shortest is 28 days — a difference that compounds across multi-month date arithmetic if month boundaries are not handled precisely.

Common mistakes to avoid

Confusing calendar days with business days for legal notices, contract periods, and planning deadlines — the distinction can shift a critical date by several days.
Not accounting for leap years when counting days across or near the end of February.
Assuming public holidays are uniform across all regions — England and Scotland have different public holidays; US federal holidays differ from state-recognised days.
Using MM/DD date notation internationally without clarifying the convention — 04/07 is April 7th in the US and 4 July in the UK, a three-month difference.

Many statutes, regulations, and contracts specify exact time periods for actions, appeals, filings, responses, and notice requirements. Missed deadlines in civil litigation (UK CPR, US Federal Rules of Civil Procedure), planning applications, employment claims, and consumer rights can result in automatic loss of rights without any substantive consideration. The Limitation Act 1980 (UK), statutes of limitations (US), and equivalent laws set time-bars on many legal claims. Always verify legally significant date calculations with a qualified legal professional, particularly for court deadlines, statutory notice periods, and contract termination dates.