Birthday Calculator
Enter a date of birth to see the weekday you were born, your age, a countdown to your next birthday and the dates you reach 10,000 days and more.
The date to count up to starts as today. Change it to see an age or a birthday on any other day.
Worked examples
10,000 days
Born 1 January 2000
Wednesday 19 May 2027
The 10,000th day after birth.
Half birthday
Born 15 May 1990
Sunday 15 November 2026
Six months after the birthday, in the year 2026.
Leap day birth
Born 29 February 2000, next birthday after 18 October 2026
Sunday 28 February 2027, turning 27
Using the 28 February choice.
About Birthday Calculator
A birthday calculator turns a date of birth into the answers people ask for: the weekday you were born on, your exact age in years, months and days, the number of days until your next birthday and the total number of days you have lived. It also gives your half birthday, six months after your birthday, which is a popular way to mark the day when a real birthday falls in the holidays, and the dates of milestones such as your 1,000th, 10,000th and 20,000th day.
The count runs up to today unless you change the second date, so you can find an age on any day, for instance the first day of a course or the date of an interview. Someone born on 29 February has a real birthday once every four years. Choose whether the other years use 28 February or 1 March and every figure follows that choice. The hours figure is days multiplied by 24, so it does not allow for the time of day you were born.
How to use Birthday Calculator
- Enter the date of birth.
- Leave the second date as today, or change it to count to another day.
- If the birthday is 29 February, choose 28 February or 1 March for other years.
- Read the age, the countdown, the days lived and the table of milestones.
Common uses
- Counting down to a birthday or planning a surprise
- Finding the date of a 10,000 day milestone
- Checking an age on a future date for an application
- Working out a half birthday for a child
Frequently asked questions
How is the age worked out?
It counts whole years from the date of birth, then whole months, then the remaining days. Someone born on 15 May 1990 is 36 years, 5 months and 3 days old on 18 October 2026.
When is a half birthday?
It falls exactly six months after the birthday. If that day does not exist, such as 31 August plus six months, the last day of the month is used.
What about people born on 29 February?
You choose whether the birthday is 28 February or 1 March in years that are not leap years. The age shown follows your choice, and a whole year is reached on that day.
Is the day count exact?
Yes, the number of days lived is the exact count of calendar days between the two dates. The hours figure multiplies that by 24 and ignores the time of day of the birth.
What is the 1,000,000,000 seconds milestone?
It is 11,574 days and about 1 hour 46 minutes, so the date shown is the day it happens, assuming a birth at midnight.