Yes — the date fields default to today, filled in by your browser.

A week numbering where week 1 contains the first Thursday of the year, so early January can fall in the previous year week 52 or 53.

Date & time Arithmetic

Date calculator

Starting date

Amount

Unit

Direction

Resulting date —

add 1 years

ISO form —

Day of the week —

ISO week —

Day of the year —

Days moved —

Note Enter a date

Add · measure · look up

Date arithmetic comes in three shapes: moving forwards or backwards from a date, measuring the gap between two, and looking up facts about one. All three are here, because the question people actually have is usually one of them and they rarely know which name it goes by.

How to use the date calculator

1 Pick whether you are adding, measuring, or looking up.

2 Dates default to today where that makes sense.

3 Every result shows the weekday, since for real decisions it usually matters.

4 Switch tabs freely — the dates carry over.

The one rule worth carrying away is that days and months behave differently. A day count is a fixed number of days; a month keeps the day-of-month number and clamps when the target month is shorter. That difference is invisible until a month-end date is involved, at which point it becomes the whole answer. Everything else in date arithmetic is bookkeeping.

Questions

What can this calculate? −

Adding to and subtracting from dates, gaps between two dates, and facts about a single date.

Does it know today? +

Are months different from 30 days? +

What is an ISO week? +

Does it handle leap years? +

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