Date Calculator

Difference, add/subtract, age, weekday — single page

Copy this file into date-calculator.html and open it.

Built for Blogger or static pages.

Start date End date

Result will appear here.

Shows absolute days, weeks and a breakdown in years, months, days (calendar-aware).

Base date Amount

Days Weeks Months Years

Result will appear here.

Calendar-aware when adding months/years (keeps day-of-month where possible).

Birth date

Result will appear here.

Age measured as full years, months, days up to today's date.

Select date

Result will appear here.

Also shows ISO week number and day-of-year.

Simple, offline, and privacy-friendly — no data leaves your browser.