Enter the birth date followed by the reference date. The reference date defaults to today, but it may also be a historical or future date. The calculator reports completed years followed by the remaining calendar months and days.
Calendar age and total days
Calendar age counts complete years, months and days. Those periods do not have equal lengths: a month may have 28 to 31 days and a leap year has 366 days. The answer therefore cannot be reproduced reliably with “years × 365.” Total days are counted directly between the two date-only values, so time of day and time zone do not affect the result.
Example
From May 15, 2000 to July 20, 2026 there are 26 complete years, two complete months and five additional days. The next birthday is May 15, 2027. For a February 29 birth date, March 1 is the birthday boundary in a year without February 29.
Result limitations
The calculator works with dates without times. It is not intended to determine an age to the exact hour or minute. Contracts and legal age thresholds may apply their own rules, which should be checked separately from the calendar result.
Frequently Asked Questions
What does a completed year of age mean?
A year is completed when the corresponding birthday is reached. Before that birthday, the current year of life is not counted as a complete year.
How are leap years handled?
The calculator uses actual calendar dates. February 29 is therefore included automatically in both total days and the calendar difference.
How is a February 29 birthday handled?
In a year without February 29, this calculation uses March 1 as the birthday boundary. The same convention is used for age and the next birthday.
Why are months not all the same length?
Calendar months contain 28, 29, 30 or 31 days. The calculator therefore counts complete calendar months instead of using a fixed number of days.
Why does the age in days not change with the time of day?
The calculator uses date-only values without a time or time zone. Each calendar day is counted as one complete day.
Can I enter a historical or future reference date?
Yes. The reference date may be before or after today as long as it is not earlier than the birth date.
How are the days until the next birthday calculated?
The calculator finds the first birthday after the reference date and counts the calendar days until that date.
