How does adding months handle the end of a month?

When the start date is near the end of a month, the result is clamped to the last valid day of the target month. So 31 January plus one month gives 28 February, or 29 February in a leap year, because there is no 31 February. This is the standard, predictable way to add months to a date.

What is the difference between adding 30 days and adding a month?

Adding 30 days always moves exactly 30 days forward, regardless of month length. Adding a month lands on the same day number in the next month, which might be 28, 30 or 31 days later depending on the month. For most "a month from now" questions, adding a month is what you want.

Can I subtract as well as add?

Yes. Switch the calculator to subtract, or enter a negative amount, to count backwards from the start date. The same month-end and leap-year rules apply, so the result is always a real calendar date.

Does this work offline and is anything sent to a server?

The calculation runs entirely in your browser, so nothing you type is sent anywhere, and once the page has loaded it keeps working with no connection. There is no sign-up and no limit on how many dates you check.

Add or Subtract Days Calculator

Add or subtract time from a date. Enter a start date and a number of days, weeks, months or years to add or take away, and the calculator shows the resulting date and the weekday it falls on. Month-ends and leap years are handled correctly. Free and instant in your browser.

Leap-year accurate
100% free
No sign-up, no app
Instant as you type
Works offline after first load

Start date

YearsMonthsWeeksDays

Result date

Monday, 15 June 2026

2026-06-15

How to use it

1
Set the start date

Pick the date you are counting from.
2
Enter the amount

Type how many days, weeks, months or years to add, or switch to subtract to count backwards.
3
Read the result

See the resulting date and the weekday it lands on, ready to use for a deadline or reminder.

When it comes in handy

Deadlines and notice

Work out a date 30 days, 90 days or a year from a start date, such as a notice period or a warranty.

Reminders and renewals

Find when something falls due by adding a fixed period to the last date.

Planning backwards

Subtract a lead time from an event date to find when to start preparing.

Instant, accurate & 100% in your browser

The calculation runs right here in your browser, counting the real calendar so leap years and month lengths come out right. Nothing you type is sent to a server, there is no sign-up and no limit, and once the page has loaded it keeps working even with no connection.

Frequently asked questions

How does adding months handle the end of a month?: When the start date is near the end of a month, the result is clamped to the last valid day of the target month. So 31 January plus one month gives 28 February, or 29 February in a leap year, because there is no 31 February. This is the standard, predictable way to add months to a date.
What is the difference between adding 30 days and adding a month?: Adding 30 days always moves exactly 30 days forward, regardless of month length. Adding a month lands on the same day number in the next month, which might be 28, 30 or 31 days later depending on the month. For most "a month from now" questions, adding a month is what you want.
Can I subtract as well as add?: Yes. Switch the calculator to subtract, or enter a negative amount, to count backwards from the start date. The same month-end and leap-year rules apply, so the result is always a real calendar date.
Does this work offline and is anything sent to a server?: The calculation runs entirely in your browser, so nothing you type is sent anywhere, and once the page has loaded it keeps working with no connection. There is no sign-up and no limit on how many dates you check.