Birthday Calculator. Enter your Date of Birth and an optional As Of Date (defaults to today) to find out your exact age in years, months, and days — plus the day of the week you were born, total days lived, and a countdown to your next birthday. Also try the Countdown Timer Calculator.
The calculator takes your date of birth and compares it to the selected 'As Of' date (defaulting to today). It computes the difference in years, months, and days using calendar-accurate logic, accounting for varying month lengths and leap years. See also our find Local Mean Sidereal Time (LST) with Sidereal Time Calculator.
Enter your birth date in the 'Date of Birth' field and leave the 'As Of Date' as today. The tool will display your exact age broken down into years, months, and days, along with your total days lived.
Yes! The Birthday Calculator automatically tells you the exact day of the week you were born — for example, Monday or Friday. Just enter your date of birth and the result appears in the 'Day of Week Born' field.
The calculator counts the exact number of days remaining from today (or your chosen 'As Of Date') to your next birthday. It also shows the calendar date of your upcoming birthday.
Yes. The calculator is fully leap-year aware. If you were born on February 29, it correctly identifies your birthday and calculates your age accordingly.
Absolutely. Use the 'As Of Date' field to enter any past or future date. This is useful for checking your age at a specific event, or to plan ahead for an upcoming milestone birthday.
Age calculations depend on the exact calendar date. If your birthday is today, you turn the new age on that day. The calculator follows the most common Western convention where age increases on the birthday itself.
Total days lived is the absolute number of calendar days between your date of birth and the 'As Of Date'. This includes leap days and gives a precise count of how many days you have been alive. You might also find our Time Duration Calculator useful.