Make sense of
the days between.

Choose a date of birth and the date to calculate for. Completed years follow the selected birthday rule. Remaining months are counted from the last birthday with month-end clamping, up to 11 months; remaining calendar days complete the result. Total days is the date difference. This is calendar arithmetic, not a legal eligibility decision.

Choose February 28 or March 1 for anniversaries in non-leap years. This controls completed years, the next birthday and its countdown. In leap years the anniversary remains February 29. The choice is a calculation convention, not a claim about the rule in a particular country.

Date difference normally reports elapsed days: the same date is zero days. Include both dates adds one to the magnitude, so the same date counts as one day. Its years/months/days breakdown still describes elapsed time. Business-day counting has separate start/end checkboxes. Adding working days always excludes the starting date; adding zero leaves it unchanged.

Years and months are combined into one month offset applied to the original date, then weeks and days are applied. Last valid day clamps a missing day to the target month-end; Reject missing day returns an error instead. For example, January 31 plus one month becomes February 28 in a common year with clamping. Reversing the operation may not recover the original date.

Saturday and Sunday are the default weekend, but every weekday can be customized. Enter your own holiday dates or import a plain TXT/CSV list of ISO dates. No country holiday database is loaded. Duplicates count once, and a holiday already on a weekend is not subtracted twice. At least one weekday must remain a working day.

No. Calculations use Gregorian calendar dates and integer day numbers, without clock times. Today uses your device’s local date at the moment you click it. This tool does not calculate elapsed clock hours, timezone conversions or historical Julian-calendar transitions.

The calculator runs in your browser without uploading the entered dates or holiday list. The last 10 successful calculations can be recalled while this page remains open; they are not saved to browser storage or encoded in links. Reports include the dates and rules you entered. Refreshing clears this temporary history.

Choose a result date, range endpoint, upcoming birthday or milestone from the calendar event selector. Export downloads one all-day ICS event, not a recurring series, and has no reminder alarm. Importing it into a calendar is a separate action; the tool does not connect to a calendar account. Calendar applications may restrict very early or very late years.

Use complete Gregorian dates from 0001-01-01 through 9999-12-31. Fractional or incomplete offsets and invalid dates are rejected. Holiday lists allow up to 1,000 entries and 16,000 text characters; imported files must be at most 20,000 bytes. Working-day offsets allow up to 1,000,000 days in either direction, within the supported date range.

Yes. Age results list up to five upcoming birthdays, including one on the reference date. Enter an optional whole-number milestone age to see its date and days before or after the reference date. February 29 birthdays follow your selected rule. Dates beyond year 9999 are not supported.