Every date calculation,
one free tool

How to use every mode

1. Date Difference — pick a start and end date (times are optional), toggle "Include end date" if your count should be inclusive, then click Calculate. You get a calendar breakdown (years/months/days) plus total days, weeks, hours, minutes, seconds, day-of-week, ISO week number, and quarter for both dates.
2. Age Calculator — enter a birth date and choose "as of today" (updates live) or a custom reference date, to get exact age, total days lived, and a live countdown to the next birthday.
3. Countdown — name an event and pick a target date/time, then click Add Countdown. Every saved countdown ticks live and can be removed individually; they're stored on this device only.
4. Add / Subtract — enter a base date, an amount, a unit (days/weeks/months/years), and a direction, to instantly find the resulting date and its day of week.
5. Business Days — pick a start/end date, choose which days count as weekends (defaults to Saturday/Sunday), optionally list holiday dates to exclude, then calculate to get a working-day total.
6. Batch — paste multiple "start, end" date pairs, one per line, and calculate all of them at once in a results table you can copy or export as CSV text.
7. Range Overlap — enter two date ranges (A and B) to check whether they overlap, and if so, see the exact overlapping period and its length.
8. Copy, share, or print — the Date Difference result panel includes buttons to copy a plain-text summary, copy a shareable link with your dates pre-filled, or print a clean report.
9. Local History — Date Difference, Age, and Add/Subtract calculations are automatically saved to this device; click any entry to reload it, or clear history at any time.

One date tool instead of a dozen

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