Find the difference between two dates, add or subtract years, months, weeks and days, get the weekday and ISO week, and see the date 30, 60 or 90 days from now.
This calculator works with pure Gregorian calendar dates, counted in whole days from 1970-01-01. That is why it is immune to time zones and daylight saving: from 2026-03-07 to 2026-03-09 is always 2 days, or 48 hours, anywhere in the world. The Gregorian calendar has 97 leap years every 400 years, which makes 146,097 days, exactly 20,871 weeks. So the weekday of a date repeats every 400 years. A year is a leap year when it is divisible by 4, except those divisible by 100, unless they are also divisible by 400. So 2000 and 2024 were leap years, but 1900 and 2100 are not. Months have different lengths, which is why "how many months between two dates" depends on a convention. Here we advance whole months from the start date and use the month's last day when the day does not exist: Jan 31 plus 1 month is Feb 28 (Feb 29 in a leap year). The convention is shown next to the result, and the totals of days, hours, minutes and seconds are exact. The ISO 8601 week starts on Monday, and week 1 of a year is the one containing the first Thursday (equivalent to containing January 4). That is why 2021-01-01 belongs to week 53 of 2020, and 2024-12-30 is already week 1 of 2025. The Gregorian calendar took effect on October 15, 1582, right after October 4, 1582 in the Julian calendar, in Catholic countries. Earlier dates are computed here with the extended Gregorian rule, the so-called proleptic calendar, which is handy for arithmetic but may differ from historical documents.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
<iframe
src="https://jkit.tools/embed/en-US/date-calculator"
width="100%"
height="600"
style="border:0"
loading="lazy"
title="Date Calculator"
></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
Subtract one date's day number from the other's. The tool does this in whole days, unaffected by time zones or daylight saving. From 2026-01-01 to 2026-12-31 is 364 days, or 365 if you also count the last day (the "Also count the last day" option).
Pick a date.
Pick a date.
Pick the dates to see the result.
The tool advances whole months from the start date without passing the end date, then counts the leftover days. When the start day does not exist in the target month (the 31st in February, for example), it uses that month's last day.
Example: from 2026-01-31 to 2026-02-28 is exactly 1 month; from 2026-01-31 to 2026-03-01 is 1 month and 1 day (Feb 28 plus 1 day). The total of days, weeks, hours, minutes and seconds is exact and does not depend on this convention.
Need to count only business days, without weekends and holidays? Use the business days calculator.
Proleptic Gregorian calendar, from 0001-01-01 to 9999-12-31, in pure dates: no time zone and no daylight saving. Before October 15, 1582 the Julian calendar was in use, so old dates here may differ from historical records.
See also: business days · countdown · age · timestamp