Date calculator, add, subtract and compare.

A date calculator does two jobs. It adds time to a date or takes time away from it, which answers questions like "what is the date 6 months and 10 days from now". It also compares two dates, which answers "how long is it from this day to that day". This one does both, in years, months, weeks and days together, and can go down to hours and minutes in a time zone of your choice.

How to add or subtract from a date

1. Open the Add or subtract tab. The Start date is today. Pick another day, or press Today to come back.
2. Choose Add or Subtract under Do.
3. Type any mix of Years, Months, Weeks and Days. Leave the others at 0.
4. Read the big card for the date and its weekday. The cards below show how far it is from today, which day of the year it is and its ISO week number. The steps list shows each move in order.
5. Press Copy result for one sentence, or Copy link for a link that opens with the same numbers.

How the order of the steps works

Years and months are added first, as calendar units, and then weeks and days. This matters at the end of a month. If the day does not exist in the new month, the last day of that month is used. Adding 1 month to 31 January 2027 gives 28 February 2027, because February 2027 has 28 days.

A worked example: start on Sunday 15 March 2026 and add 1 year, 2 months, 3 weeks and 4 days. Add 1 year and 2 months first, which is 14 months, and you land on Saturday 15 May 2027. Then add 3 weeks and 4 days, which is 25 days. From 15 May, 16 days takes you to 31 May and 9 more to 9 June. The answer is Wednesday 9 June 2027, the 160th day of 2027 (31 + 28 + 31 + 30 + 31 = 151 days to the end of May, plus 9), in ISO week 23.

How to find the gap between two dates

1. Open Between two dates and pick the Start date and the End date. The arrows between them swap the two.
2. Switch on Count the end date too when both the first and the last day should count, such as the days of a trip.
3. Read the big card for years, months and days, then the cards for the total days, weeks, hours, minutes and seconds.

Example: from 14 February 2026 to 4 July 2026. Counting whole months from the 14th, you reach 14 June after 4 months. From 14 June to 4 July is 20 days. In days that is 28 + 31 + 30 + 31 = 120 days to 14 June, plus 20, which is 140 days, or exactly 20 weeks. If the end date is earlier than the start date, the calculator swaps them and says so.

Including a time of day

Tick Include a time of day to add the Start time, the Hours, Minutes and Seconds boxes, and a Time zone. It starts on your own time zone. The rule is simple: days, weeks, months and years keep the same clock time, and hours, minutes and seconds are real time.

The United States clocks went forward at 2:00 a.m. on 8 March 2026 (NIST daylight saving page, checked 24 Oct 2026). Start in New York at 1:30 a.m. on 8 March 2026. Adding 1 day gives 1:30 a.m. on 9 March, but only 23 real hours pass, because one hour was skipped. Adding 24 hours gives 2:30 a.m. on 9 March, because 24 real hours were needed. The page shows a note whenever a clock change makes the two differ.

Month ends are where date maths goes wrong, so here is how this page treats them:

Common problems

• A time that does not exist. If you land on a clock reading the clocks skipped, the page shows the time after the jump and says so. Add 1 day to 2:30 a.m. on 7 March 2026 in New York and you reach 2:30 a.m. on 8 March, which never happened, so it is shown as 3:30 a.m.
• A time that happens twice. When the clocks go back, one hour repeats. The first of the two is used.
• A different answer from another site. Some tools add days before months, or use 30 day months. This page adds years and months first and uses real calendar months.
• Working days. This page counts every day. For Monday to Friday and holidays, use days between dates.

For a quick answer from today, try 30 days from today or 3 months from today. To measure a person's age to the day, use the age calculator.