Online age calculator, calculate exact age

What is this online age calculator?

It is a free online age calculator that was made by the 'PU Tools' developer team. The number of uses is unlimited without any registration requirement.

Have you ever been curious about your (or someone's or some event's) exact age in years, months, and days 🤔? This tool will give you the exact details based on your given birthdate.

It is not only used to calculate age from the date of birth to the current date, but also calculates to another specific date.

It is also used to calculate age from the start date to the end date of an event (for example, the age of a course).

By default, the 'Today or another end date' field will be the current date of your device (we can call it 'today').

To guarantee it can calculate age smoothly, please enter a valid start date and end date.

Below is the test vector of this age calculator:

How to use this tool?

Step 1: Enter 'Date of birth or another start date' and 'Today or another end date' in the provided fields. You can type them directly or use the date picker.

Step 2: After entering your dates, click the 'Calculate' button.

Step 3: View and share your exact age in years, months, weeks, days, hours, minutes and seconds.

How useful is this tool?

✔️ Personal or something's age: View the exact age of you or someone or some event in different time units.

✔️ Age difference: Calculate the age difference between two persons. Enter two birthdates into the 'start date' and 'end date' fields, and you'll know the difference.

✔️ Elapsed time: Determine the time elapsed between events (for example: course's start date and end day).

How to calculate in detail (year, month, day) using mathematics?

Necessary and sufficient conditions: The end date must be after the start date.

We set Y1 = start year, Y2 = end year, M1 = start month, M2 = end month, D1 = start date, D2 = end date.

Next, we take Y = Y2 - Y1, M = M2 - M1, D = D2 - D1.

If D is negative, then M will subtract 1 and add the number of days of the previous month to D.

If M is negative, then Y will subtract 1 and add 12 months to M.

Example: Suppose we want to calculate from 05/15/1990 to 07/10/2023:

Preliminary calculation: Y = 2023 - 1990 = 33; M = 07 - 05 = 2; D = 10 - 15 = -5.

Adjust the date:

• Because D is negative, we will move back 1 month from the calculated month number: 2 months → 1 month.
• The month immediately before July is June. June has 30 days.
• New number of days: -5 + 30 = 25.
• So, temporarily we have: 33 years, 1 month, 25 days.

Adjust the month:

• The current month number is 1, not negative. So there is no need to adjust the year or month.

Final result: That person (or event) has existed for 33 years, 1 month, and 25 days.