Add days to a date

Start from a date, add or take away days, weeks, months or years, and see where you land.

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Common date math from November 4, 2026

Notice that 180 days and 6 months land on different dates. Months have different lengths, so "6 months" and "180 days" are only roughly the same; when a contract or a rule names one of them, use that one.

Where this comes up

• Deadlines and notice periods: "within 30 days of the invoice", "60 days' notice". If the deadline counts working days instead, use the business days calculator.
• Returns and warranties: a 90-day return window or a 1-year warranty from the purchase date.
• Medication and health: a follow-up in 6 weeks, a course that lasts 14 days.
• Travel and visas: how many days a stay allows, or when a 180-day period ends. Visa rules often count the arrival day too, so check the exact wording.
• Milestones: 100 days since a launch, 1,000 days since you met, 10,000 days old.

How it adds

Years and months go first, then weeks and days. Adding 1 month to January 31 gives February 28 (or 29 in a leap year), because February has no 31st. The calculator never rolls over into March.

Leap days are handled the same way: one month after January 31, 2028 is February 29, because 2028 is a leap year, and one year after February 29, 2028 is February 28, 2029.

Days are calendar days, so weekends and holidays count. "30 days from today" lands on the same date whether or not a holiday falls in between.

Weeks, months and years

Weeks are always seven days, so 6 weeks from a Wednesday is also a Wednesday, 42 days later. Months and years follow the calendar instead of a fixed number of days: adding 1 month to March 15 gives April 15 whether the month has 30 or 31 days, and adding 1 year keeps the same date in the next year. You can combine fields, for example 1 year and 2 weeks, and the calculator applies years and months first and then weeks and days.

Month ends and weekends: worked cases

These are the cases that most often surprise people. Each result, and the note under it, is what the calculator shows.

Going one month at a time does not undo itself. January 31 plus one month is February 28, but February 28 plus one month is March 28, not March 31, so adding "1 month" twice is not always the same as adding "2 months" once (January 31 plus 2 months is March 31). When a payment or a renewal is due "on the last day of each month", work from the original date each time rather than from last month's result. The 30, 60 and 90 day, 6 month and 1 year buttons fill the fields in one tap.

Questions

What if the result falls on a weekend?

The calculator still gives the calendar date, because that is what "30 days" means, and adds a line with the next weekday. Many deadlines that end on a weekend or holiday roll to the next working day, but not all do, so check the rule you are working with. To count only working days from the start, use the business days calculator.

Does "30 days from today" include today?

No. Counting starts tomorrow, so 1 day from Wednesday is Thursday. This matches how most deadlines and return windows are written.

Can I go back in time?

Yes. Choose Subtract to find the date a set number of days, weeks, months or years before the start date.

Last updated November 5, 2026 · Spotted a wrong result? Tell us and we'll check it.