AGE & DATE CALCULATORS
Every day counts.
Find how many days you have lived, with leap years included.
Age in Days Calculator
Simple inputs. Precise calendar results.
Your dates are processed locally in your browser and are not stored.
A TOOL FOR EVERY DATE
More ways to count time.
THE DETAILS MATTER
Calendar maths,
without the guesswork.
We count complete calendar years first, then complete months, then the days left over. We never estimate your age by dividing milliseconds by 365.
How are leap years and 29 February handled?
1900 is not a leap year; 2000 is. For a 29 February birth, the anniversary is 28 February in non-leap years. This is a calculation convention, not a rule for legal age.
What happens at the end of a month?
When a calendar step lands beyond the end of a month, we use that month’s last day. For example, 31 January to 28 February 2001 is one complete month. Total months means years × 12 plus the remaining complete months in this calendar breakdown.
Are the start and end dates both counted?
We measure elapsed time: the same date is zero days; 1 January to 2 January is one day. Weeks are complete groups of seven days. Hours are approximate, using 24 hours per day without time of birth or daylight saving changes.
Which date is used for my next birthday?
Your next birthday is calculated from “Calculate Age On”. If that date is your birthday, the countdown is zero. Today comes from your device’s local calendar; calculations then use date-only UTC values to avoid time-zone shifts.
How does the birth year calculator work?
If you have had your birthday this year, subtract your age from the current year. Otherwise subtract one more year. If you are unsure, both possible years are shown when possible. On 31 December, everyone has already had their birthday under this calendar convention.