Date Calculator — Add to or Subtract From Any Date
This date calculator adds days, weeks, months, or years to any start date, or subtracts them, and tells you the exact resulting date including the day of the week. Pick a start date (or press Today), choose Add or Subtract, enter the amount and unit, and press Calculate. It handles leap years and month-end dates correctly, and warns you when the result lands on a weekend.
How Date Addition Works
Adding days and weeks is plain counting: every calendar day counts, including Saturdays, Sundays, and holidays, and a week is always exactly 7 days. Adding 10 days to June 25 rolls over the end of the month and lands on July 5, and adding 2 weeks always lands on the same weekday you started from.
Months and years are trickier because they are not all the same length. The standard rule, which this calculator follows, is to keep the same day of the month and clamp to the end of the month when that day does not exist. January 31 plus 1 month becomes February 28 (or February 29 in a leap year), because February has no 31st. March 31 plus 1 month becomes April 30. The same applies to years: February 29, 2024 plus 1 year becomes February 28, 2025, since 2025 is not a leap year.
Leap years themselves are handled automatically. A year divisible by 4 is a leap year, except century years, which must be divisible by 400 — so 2024 and 2028 are leap years, while 2100 is not. Any day-counting that crosses February 29 simply includes it as one more calendar day.
Common Uses for a Date Calculator
Most date math questions are really deadline questions. Contracts and invoices often give you "net 30" or "net 60" payment terms, returns and refunds usually have a 30- or 90-day window, and many visas, ESTA-style travel authorizations, and tourist stays are limited to 90 or 180 days. Counting forward from a start date tells you exactly when the window closes, weekday included, so you know whether the deadline lands on a workday.
Week-based counting is just as common: pregnancy is tracked in weeks from a known start date, training plans run in week blocks, and notice periods are often "4 weeks from today". Because a week is exactly 7 days, week addition always lands on the same weekday, which makes scheduling recurring events easy.
Keep in mind that calendar days are not working days. If your deadline counts business days only, use our business days calculator, which skips weekends and can exclude holidays. And if you need the gap between two known dates rather than a date offset, the time duration calculator gives the exact difference in years, months, and days.
Days From Today — Quick Answers
Looking for a specific count from today's date? These pages show the live answer for the most common day counts, including the weekday it lands on:
Frequently Asked Questions
Enter the start date in the calculator above, choose Add, type 30, set the unit to Days, and press Calculate. The result shows the exact date 30 calendar days later, including the day of the week. By hand, you can add 30 to the day of the month and roll any overflow into the next month.
Click the Today button to set the start date to today, choose Add, enter 90, and select Days. Because the answer changes every day, the tool calculates it live in your browser. We also have a dedicated 90 days from today page with the current answer.
Yes. This calculator counts every calendar day, including Saturdays, Sundays, and holidays. If you need working days only, use our business days calculator instead, which skips weekends and can exclude holidays.
The calculator clamps to the last day of the target month. For example, January 31 plus 1 month gives February 28 (or February 29 in a leap year), because February has no 31st. The same rule applies to year addition: February 29 plus 1 year gives February 28.
This tool adds an amount to or subtracts an amount from a single date. To find the gap between two specific dates, use our time duration calculator, which gives the difference in years, months, days, and more. For working days between two dates, use the business days calculator.