Date calculator
Find the days between two dates, or add and subtract time from any date. Runs entirely in your browser, nothing is sent to a server.
How the calculation works
Counting days sounds simple until you hit a month with 28 days instead of 30, or a leap year that adds one back in. This calculator uses the actual Gregorian calendar, not a fixed 30-day-month approximation, so results stay accurate across February, leap years, and year boundaries.
Adding a month to a date isn't always the same number of days. "One month from January 31" is commonly interpreted as February 28 (or 29 in a leap year), since February has no 31st day — the month rolls forward and the day clamps to the last valid date. This calculator follows that convention.
Business day counts exclude Saturdays and Sundays by default. For calculations that also need to exclude public holidays for a specific country, use the business days calculator.
Common questions
What is datecalculator.site?⌄
datecalculator.site is a free set of date calculation tools. On this homepage you can find the number of days between two dates, add or subtract time from a date, and jump to common shortcuts like 30, 60, or 90 days from today — all in one place, calculated instantly in your browser.
How do I calculate the number of days between two dates?⌄
Open the "Days between" tab, pick a start date and an end date, and the total number of days appears immediately, along with a breakdown into years, months, and weeks, plus business days and the day of the week each date falls on.
How do I calculate the number of weeks between two dates?⌄
Use the "Days between" tab the same way — the result includes a weeks-and-days breakdown alongside the total day count, so you don't need a separate weeks-only calculator.
What does the add/subtract date tool do?⌄
The "Add/subtract" tab takes a starting date plus a number of days, weeks, months, or years, and gives you the resulting date — useful for things like working out a deadline, a due date, or an anniversary a set amount of time from a known date.
What does the quick shortcuts tool do?⌄
The "Quick shortcuts" tab gives you one-click answers for common intervals like 30, 60, or 90 days from today, plus a custom field if you need a different number of days, weeks, or months — no need to look up today's date and do the math yourself.
What makes this date calculator better?⌄
It's fast, accurate across leap years and variable month lengths, and runs entirely in your browser with no data sent to a server. The three tools — days between, add/subtract, and quick shortcuts — cover most real-world date questions from a single page, with extra detail like business days and day-of-week included by default rather than hidden behind extra clicks.
Does the days-between calculation include the end date?⌄
No. The result is the number of days from the start date up to but not including the end date — the same convention used for lease terms, age, and most legal deadlines. If you need an inclusive count, add one day to the result.
What's the difference between calendar days and business days?⌄
Calendar days count every day, including weekends. Business days exclude Saturdays and Sundays. Contract deadlines, payment terms, and legal filing windows often specify one or the other explicitly — check the relevant document before assuming.
Why does adding one month sometimes change the day of the month?⌄
Months have different lengths. Adding one month to January 31 can't land on February 31, since it doesn't exist — this calculator rolls forward to the last valid day of the target month (February 28, or 29 in a leap year).
Is my date data sent to a server?⌄
No. All calculations run locally in your browser using JavaScript. Nothing about the dates you enter is transmitted or stored.