Free Date Calculator - Calculate Date Difference & Add Days Online

A You can easily estimate your pregnancy due date. If you know the first day of your last menstrual period (LMP), select 'Date Addition' mode. Enter your LMP as the 'Start Date', choose 'Add', enter 280, and select 'Days' as the unit. The resulting date will be your estimated due date, commonly known as your 'expected date of delivery' (EDD).

A To find a date X months and Y days from a start date, use the 'Date Addition' mode. First, enter your start date, select 'Add', specify the number of months, and click calculate. Then, take that result date, re-enter it as the new start date, select 'Add' again, specify the number of days, and calculate. This two-step process provides your precise combined future date.

A Our calculator treats calendar months by advancing the month and keeping the day the same, so January 15th plus one month is February 15th. However, when calculating the *difference* between two dates, a month is often approximated as 30 days for simplicity, especially if the dates fall on the same day of consecutive months. This provides a quick, general estimate.

A Absolutely. Switch to Date Subtraction mode, pick your start date, then choose 'Weekdays' as the unit. Enter the number of business days you need to go back. The calculator skips weekends automatically. For example, subtracting 5 weekdays from a Friday lands you on the previous Friday. Handy for invoice due dates or contract lookbacks.

A That's the calendar month rule in action. Add 1 month to Nov 30 and you get Dec 30. Add another to Dec 30 and you get Jan 30. The third addition lands on February 30th—but that date doesn't exist. So the calculator snaps to the last valid day of the month, which is Feb 28 (or Feb 29 in a leap year). This follows standard business and legal date math. If you need exactly 90 days instead, use the Days unit and enter 90.

A You can go from January 1, 0001 to December 31, 9999. That covers just about any historical or future need. For example, finding the day of week for July 4, 1776 works fine. The only catch: dates before October 1582 follow the Julian calendar, not Gregorian. Most people never hit this edge case, but historians should know. Pro tip — your browser might complain if you pick a year with three digits, but the tool handles it.

A Yes, switch to Date Difference mode and look for the 'Weekdays only' toggle. This excludes Saturdays and Sundays from the count. Handy for contract lawyers tracking business days or anyone planning a project timeline. For example, from Monday to the following Monday, you get 5 weekdays, not 7. Just remember it doesn't account for holidays — you'll need to adjust for those manually.

A This usually happens because of time zones. Our calculator works with calendar dates, not specific hours. If someone was born at 11 PM UTC but you're in Tokyo, your local date might be a day ahead. The tool doesn't adjust for birth time or location. For forms like passport applications or legal documents, just use the date of birth and the target date exactly as written. That gives you the correct calendar-age every time.

A No account, no install, no login. Just open the page and start typing dates. Everything runs in your browser, so your data never leaves your device. That also means it works offline if you save the page or bookmark it. For repeated use, add it to your browser's bookmarks bar—it loads in under a second. One tip: if you're on a phone, rotate to landscape for a better view of the week/month breakdown.

A Yes, it does. The tool follows the standard Gregorian calendar rules, so February 29th only appears in leap years. For example, adding 1 year to February 29, 2024 gives you February 28, 2025—not March 1st. The same logic applies when calculating differences: the span from March 1, 2023 to March 1, 2024 counts as exactly 366 days because 2024 is a leap year. You won't need to adjust anything manually, whether you're planning a multi-year project or just checking a birthday.