Find your exact age or the time between any two dates — down to the day
This tool is for: People verifying their exact age for legal or official purposes · Anyone counting days to a milestone, birthday, or deadline · Parents tracking a child's age in months and days
- Your exact age in years, months, and days
- How old you will be on any future date
- The exact duration between any two dates in days, weeks, months, and years
Formulas Used
Days Between Two Dates
Total Days = (Date2 - Date1) / (1000 × 60 × 60 × 24)
Where: Date1 = Start date as milliseconds since epoch (milliseconds), Date2 = End date as milliseconds since epoch (milliseconds), Total Days = Number of calendar days between dates (days)
Source: Standard date arithmetic using Unix epoch time ✓ Verified
Age Calculation (Year/Month/Day Breakdown)
Iterative calendar subtraction: years = endYear - startYear, adjusted for month/day overflow
Where: years = Completed full years (years), months = Remaining completed months (months), days = Remaining days (days)
Source: Standard calendar arithmetic with Gregorian calendar rules ✓ Verified
Key Insight
Your legal age typically changes at midnight on your birthday, not at your exact time of birth. However, a few jurisdictions use the day before your birthday as the day you reach the new age — if this matters for a legal threshold, verify with the relevant authority. For most US contexts, the midnight rule applies.
How Changes Affect Your Result
calendar definition of 'one month': If you compute duration as 'months × 30 days', you get a different answer than calendar arithmetic for long durations. For a 5-year span, 30-day months give 1800 days but actual calendar arithmetic gives ~1826 days (with leap years). For contracts, leases, and ages always use calendar arithmetic — never the 30-day approximation.
Frequently Asked Questions
How do leap years affect age calculation?
Leap years add February 29th every four years (with exceptions for century years not divisible by 400). If you were born on February 29th, your age in years still increments each year — you turn one year older on March 1st in non-leap years, or on February 29th in leap years. The total days alive calculation accounts for all leap years between your birth date and today, so the day count is always accurate. For example, someone born on Feb 29, 2000 turns 26 on March 1, 2026, having lived through 6 leap years (2000, 2004, 2008, 2012, 2016, 2020, 2024).
Does my age change at midnight or at my exact birth time?
In virtually all legal and practical contexts, your age changes at midnight (12:00 AM) on your birthday. For example, if you were born at 3:47 PM on June 15, you legally turn one year older at the start of June 15 the following year, not at 3:47 PM. There are rare legal exceptions — some jurisdictions in specific contexts (such as drinking age enforcement) may interpret age differently, but the midnight convention is the overwhelming standard. This calculator uses the midnight convention.
How does this calculator handle months of different lengths?
Calendar months range from 28 to 31 days, which makes month-based calculations slightly ambiguous. This calculator uses calendar month arithmetic: it counts the number of complete months that have passed and then counts remaining days. For example, from January 31 to March 2 is 1 month and 2 days (January 31 to February 28/29 is one month, plus 2 more days to March 2). This matches how people naturally think about months and is the same method used by most official age calculation standards.
About This Calculator
Sources:
- timeanddate.com — Date Duration Calculator — Date arithmetic methodology and expected results for date duration calculations
- MDN Web Docs — JavaScript Date Object — Date parsing, arithmetic, and leap year handling in the JavaScript runtime
Limitations:
- Uses Gregorian calendar only — does not support lunar, Islamic, Hebrew, or other calendar systems
- Does not account for time zones — uses date-only calculation assuming local dates
- Leap year handling is included (Feb 29 birthdays are handled correctly)
- Does not account for historical calendar changes (e.g., Julian to Gregorian transition)
- Age is calculated as of midnight — it does not consider birth time
When to consult a professional: For legal age determination in jurisdictions with specific rules (such as whether age changes at midnight or at the exact birth time), consult a legal professional.
This age calculator uses Gregorian calendar arithmetic and JavaScript's Date object for date computations. Results are based on date-only calculations without regard to time of day or time zone. For legal age verification, confirm requirements with the relevant authority as some jurisdictions calculate age differently.