Date of Birth Calculator

What Is a Date of Birth Calculator?

A Date of Birth Calculator is an online age calculator that determines how old a person is based on their date of birth. Enter a date of birth and a calculation date to find the person's calendar age in years, months and days.

The calculator can also show the total elapsed time between the two dates in days, weeks, hours, minutes and seconds. By default, it uses today's date, but another date can be selected when you want to determine an age at a particular point in the past or future.

Why Use the Date of Birth Calculator?

Calculating an exact age manually can be difficult because months have different numbers of days and leap years affect the number of days between dates. This calculator handles those calendar differences automatically.

How to Use the Date of Birth Calculator

Enter your date of birth and the date on which you want your age calculated. The calculator will then display your calendar age and additional elapsed-time measurements.

1. Enter your date of birth — Select your birth date using the date field.
2. Choose the calculation date — Today's date is selected automatically, or choose another date if required.
3. Calculate your age — Select Calculate Age to process the two dates.
4. Review the results — View your age in years, months and days and see the total elapsed time in other units.

How Is Age Calculated From a Date of Birth?

Age is normally expressed as the number of complete years, followed by the remaining complete months and days. For example, someone may be 30 years, 4 months and 12 days old on a particular date. This calendar-based result is different from simply dividing the number of elapsed days by 365.

The Date of Birth Calculator compares the calendar components of the birth date and calculation date. It accounts for the different lengths of months and leap years to produce a calendar age that reflects the actual dates entered.

Calculating Age Between Two Dates

Although most people use a Date of Birth Calculator with today's date, the same calculation can be performed using any two valid dates. This makes the tool useful for determining how old someone was on a previous date or how old they will be on a future date.

Age in Days, Weeks, Hours, Minutes and Seconds

The calculator also provides the total elapsed duration between the two selected dates. Total days are based on complete calendar days between the dates, while the week, hour, minute and second figures are derived from that elapsed duration. These measurements are useful when a calculation requires a total rather than a calendar age.

Date of Birth Calculator Accuracy and Limitations

The calculator performs its calculations entirely in your web browser. Your entered date of birth is not submitted to a YesTools server by this tool. Results depend on the dates entered and the calendar rules used by the browser's date handling.

The years, months and days result represents calendar age rather than an approximation based on a fixed number of days per year. This distinction is important because calendar years can contain 365 or 366 days and calendar months contain different numbers of days.

Frequently Asked Questions