A February 29 anniversary
For someone born February 29, 2000, the completed-year count on February 28, 2026 is 26 with the February 28 policy and 25 with the March 1 policy. Under the latter, the next birthday is one day away.
The as-of date is a birthday under the selected policy.
9,496Whole calendar days since birth
1,356Completed seven-day weeks
365Days until next birthday after as-of date
Next birthday: 2027-02-28
Last annual anniversary: 2026-02-28. Completed months are measured from that date with shorter months clamped to their last day; remaining days begin at 2026-02-28. This is a date calculation, not a legal age determination.
Calculations run in your browser. Dates and settings are not uploaded by this tool.
How to use the Age Calculator
- 01
Enter the date of birth and a date on or after it. Use Age today to fill the as-of date from your device’s local calendar.
- 02
Choose whether February 29 anniversaries fall on February 28 or March 1 in common years. This is a calculation preference.
- 03
Read the completed calendar age, total calendar days, and next birthday after the as-of date. Copy the result with the policy attached.
Examples
Calendar months are not fixed day blocks
From January 31 to March 30, 2023, this method reports 0 years, 1 month, and 30 days. One month reaches February 28 after clamping; the remaining days then run from that anchor to March 30.
How the calendar age is built
First the tool finds the number of completed annual anniversaries under the chosen leap-birthday policy. It then advances whole months from that annual anchor, always using the original anchor day and clamping shorter months, up to eleven completed months. Finally it counts calendar dates from the last month anchor to the as-of date. The result shows both anchors so the decomposition can be audited.
Total days and calendar age describe different things
Total days is the ordinary date difference without counting the birth date as an extra day. Completed weeks are groups of seven of those days. Years and months vary in length, so multiplying the reported age by 365 or 30 will not reconstruct the day total. Time of birth, time zones, and the fraction of the current date are not part of this calculation.
The birthday policy is not a legal rule
The two February 29 choices make an otherwise hidden assumption explicit. They do not determine a legal age, eligibility date, benefit entitlement, or official birthday in any jurisdiction. Use the policy required by the system you are comparing against, and verify official requirements separately when they matter. On an anniversary date, the next-birthday field points to the following anniversary.
What to know
- Date-only, proleptic Gregorian calculation for years 0001–9999. Not a legal age determination.
Common questions
Why can another calculator report a different month and day remainder?
Calendar-duration decompositions depend on their anchoring and month-end conventions. This tool uses the last annual anniversary, then month shifts from that anchor, then remaining days. Its anchors appear beside the result.
Does the as-of date update automatically?
The initial dates are a fixed example. Age today explicitly loads your device’s current local date, and the result stays tied to the date displayed in the input.
Can birth and as-of dates be the same?
Yes. The age and total day count are zero. An as-of date earlier than birth is rejected.