Date & Age Calculator

Differences, date arithmetic, exact age, live countdowns, ISO weeks — instant results, fully offline.

Days between dates

Order doesn't matter — dates are swapped automatically.

First date

Second date

Exclude weekends (working days skip the start date, same as days between)

0 days

Years, months, days—

Weeks + days—

Working days (Mon–Fri)—

Month math clamps correctly: Jan 31 + 1 month = Feb 28/29.

Start date

Amount

Unit

—

ISO date—

Day of week—

Exact age at any reference date (defaults to today). Born on 29 Feb: next birthday is 28 Feb in non-leap years (date is clamped).

Birth date

As of (optional)

—

Total months—

Total weeks—

Total days—

Born on a—

Next birthday—

Live countdown — save up to 10 named countdowns (stored locally).

Name

Date

Time

days

hours

min

sec

ISO 8601 week numbering (weeks start Monday).

Date

ISO week—

Day of year—

Quarter—

Leap year—