What is the Age Calculator Between Two Dates?

The age calculator between two dates tells you the exact time that has passed from one date to another, in completed years, months and days. Most people use it to find their own age from a date of birth, but it works for any two dates: a joining date and today's date, a marriage date and an anniversary, or the birth dates of two people. If you have been searching for a free age calculator between two dates that needs no signup, this tool is built for that. Enter a start date and an end date and the result appears instantly.

Calculating age by hand looks easy until months have 28, 29, 30 or 31 days and leap years get involved. This is where most manual mistakes happen. The calculator handles the calendar for you, so the age calculation between two dates is accurate every time. Along with years, months and days, it also shows the same gap as total months, weeks, days and hours, which is useful when a form asks for age in one particular unit.

Because both dates are editable, you are not limited to "age today". You can calculate age as on a cut-off date for a government exam, age at the time of an event, or the age difference between two people. All calculations run in your browser and nothing you enter is stored.

How to use the age calculator between two dates

You can calculate age between two dates in a few seconds. Follow these steps:

1. Start date: enter the earlier date. For your own age this is your date of birth (DOB). For service or relationship duration it is the joining date or the event date.
2. End date: enter the later date. Use today's date for current age, or pick any other date to find age "as on" that day, such as an exam cut-off date or a form deadline.
3. Include end date (optional): if your rule counts both the first and the last day, tick this option. It adds one day to the result. Most age rules do not need it, but some service records do.
4. Press Calculate: the result shows your age in years, months and days, followed by the same period in total months, weeks, days and hours.
5. Check and use the result: keep the end date and the start date in the correct order. If the end date is earlier than the start date, swap them.

The result works as a standard calendar age. For admissions, jobs, insurance or legal documents, the final age is always the one decided by the official authority and the rules it follows, so confirm with the notification or form instructions.

Formula: how age calculation between two dates works

The calculator uses the same method as a manual calendar calculation. It subtracts the start date from the end date part by part and borrows from the previous month or year when a part turns negative. In short:

Years  = End Year  − Start Year
Months = End Month − Start Month
Days   = End Day   − Start Day

If Days < 0   → Months = Months − 1
              and Days = Days + (days in the month before the end month)
If Months < 0 → Years  = Years  − 1
              and Months = Months + 12

Total Days   = End Date − Start Date
Total Weeks  = Total Days ÷ 7
Total Months = (Years × 12) + Months
Total Hours  = Total Days × 24

The "borrow" step is the part people usually get wrong. If the end day is smaller than the start day, one full month is taken back and its days are added to the day count. The number added is the length of the month that comes just before the end month, so it can be 28, 29, 30 or 31.

Step-by-step manual example

Let us calculate the age from 10 March 2000 to 5 January 2026, a case where borrowing is needed.

As a check, the same period equals 9,432 days in total, which you get by subtracting the two dates directly.

Solved examples of age between two dates

The table below shows common date pairs and their results, so you can compare them with your own calculation.

Notice the 6-year gap from 1 Jan 2020 to 1 Jan 2026. It is 2,192 days, not 2,190, because two leap days (29 Feb 2020 and 29 Feb 2024) fall inside the period.

Leap years and month-end dates

A normal year has 365 days. A leap year has 366 because February gets an extra day. The rule is simple: a year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400. So 2000 and 2024 are leap years, while 1900 and 2100 are not.

Two situations can change the answer by a day, depending on which method is used:

• Born on 29 February: in non-leap years some systems treat 28 February as the birthday and others treat 1 March. Check which one your form or department follows.
• Month-end dates: when the start day is 29, 30 or 31 and the target month is shorter, different tools may count the leftover days slightly differently. The total number of days is always the same.

Age in months, weeks, days and hours

Sometimes a form needs your age in one unit only. Using the first example (15 Aug 1998 to 23 Oct 2026), the same age looks like this:

Age difference calculator between two dates (two people)

You can also use this tool as an age difference calculator between two dates. Put the older person's date of birth in the start field and the younger person's date of birth in the end field. The result is how much older one person is than the other. It stays the same on every day of the year, so you only need to calculate it once.

This is handy for siblings, couples, parent and child comparisons, school class age gaps and family tree records.

How to calculate age between two dates in Excel

If you work with many dates, Excel is a good place to calculate age. The key function is DATEDIF. It is not listed in the function wizard in many versions, but it works when typed, including older versions such as Excel 2007, and it also works in Google Sheets. Put the start date in cell A2 and the end date in cell B2.

Age calculation formula in Excel between two dates (years, months and days)

To show the full age in one cell, join the three parts together:

=DATEDIF(A2,B2,"Y")&" years, "&DATEDIF(A2,B2,"YM")&" months, "&(B2-EDATE(A2,DATEDIF(A2,B2,"M")))&" days"

This returns 28 years, 2 months, 8 days for the example dates. You can use DATEDIF(A2,B2,"MD") for the days part, but Microsoft notes that the "MD" option can give wrong or negative results in some cases, so the EDATE version above is safer.

How to calculate age difference between two dates in Excel

The method is the same. Put the two dates of birth in A2 and B2 (older first) and use the full formula above. If you only need the gap in days, =ABS(B2-A2) is enough.

Quick approximate formula

For a rough age in years that does not need DATEDIF, use =INT((B2-A2)/365.25). The 0.25 accounts for leap years on average. It can be off by a day around birthdays, so use DATEDIF when you need exact age.

Where the age calculator between two dates is useful

An accurate date difference is needed more often than people expect. Here are the most common cases:

For job experience between two dates, our Experience Calculator gives the same kind of result in a format built for resumes and service records.

Age calculator between two dates for astrology

People who read horoscopes and birth charts often need the exact age at the time of an event, for example age at marriage, at a job change or when a planetary period (dasha) starts or ends. For this, put the date of birth in the start field and the event date in the end field. The calculator gives the age in years, months and days at that event, which you can match against your chart.

Keep in mind that this tool works on calendar dates only. It does not prepare a kundli or consider birth time and place. Some astrologers also count age in a different way, such as running age, which counts the year in progress as complete. If you follow such a system, confirm the method with your astrologer before using the result.

Common mistakes when calculating age between two dates

• Subtracting years only: 2026 − 1998 = 28 is only correct if the birthday has already passed in the end year.
• Assuming every month has 30 days: this gives wrong day counts. Use the real length of the month, as in the borrow step.
• Forgetting leap days: a six-year gap can have 2,190 or 2,192 days depending on how many 29 Februaries fall inside it.
• Mixing date formats: 05/03/2026 is 5 March in India and the UK but 3 May in the US. Always check the day-month order.
• Counting the end date by mistake: most age rules do not count it. Include it only when a rule says so.
• Swapping the dates: the older date must be the start date, or the result will be negative or invalid.

Frequently asked questions

=DATEDIF(A2,B2,"Y")&" years, "&DATEDIF(A2,B2,"YM")&" months, "&(B2-EDATE(A2,DATEDIF(A2,B2,"M")))&" days"

LocalDate start = LocalDate.of(1998, 8, 15);
LocalDate end   = LocalDate.of(2026, 10, 23);

Period p = Period.between(start, end);
int years  = p.getYears();    // 28
int months = p.getMonths();   // 2
int days   = p.getDays();     // 8

long totalDays = ChronoUnit.DAYS.between(start, end);  // 10296

#include <stdio.h>

int is_leap(int y) { return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0); }

int days_in_month(int m, int y) {
    int d[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    return (m == 2 && is_leap(y)) ? 29 : d[m - 1];
}

int main(void) {
    int d1 = 15, m1 = 8, y1 = 1998;   /* start date */
    int d2 = 23, m2 = 10, y2 = 2026;  /* end date   */

    int years = y2 - y1, months = m2 - m1, days = d2 - d1;

    if (days < 0) {
        int pm = (m2 == 1) ? 12 : m2 - 1;
        int py = (m2 == 1) ? y2 - 1 : y2;
        months--;
        days += days_in_month(pm, py);
    }
    if (months < 0) {
        years--;
        months += 12;
    }

    printf("%d years, %d months, %d days\n", years, months, days);
    return 0;
}