Free Days Between Dates Calculator
Count the exact number of days, weeks, and months between any two dates.
What is a days between dates?
A days between dates is a free online tool that helps you calculate the exact number of days, weeks, or months between any two dates. It runs entirely in your browser — no signup, no app, and no data is ever sent to a server.
I've been burned by counting days on a calendar by hand more times than I care to admit — missing a deadline by one day because I forgot March has 31 days, not 30. Need to know exactly how many days between two dates? Maybe for billing, legal deadlines, a project timeline, or just curiosity. Pick any start and end date and the calculator gives you days, weeks, months, and years apart. It also handles business days only (weekdays), inclusive/exclusive counting, and even includes hours and minutes if you need that level of detail.
How it works
The calculation subtracts the earlier date from the later date to get the total number of milliseconds, then divides by 86,400,000 (the number of milliseconds in a day) to get the day count. Leap years are automatically handled since the calculation works with actual calendar dates rather than fixed year lengths. Optional time inputs let you calculate the exact difference down to hours and minutes — perfect for tracking project deadlines with hourly precision.
For example, the number of days between January 1 and December 31 of the same non-leap year is 364. Between January 1 and December 31 of a leap year, it is 365, because February 29 adds one extra day. The calculator also shows the result in weeks, months, and years for convenience. The "Include end date" checkbox switches between exclusive counting (the default, which does not count the end date) and inclusive counting, which adds the end date to the total.
A business-days-only mode excludes weekends (Saturdays and Sundays) from the total — useful for calculating workdays between two dates for project planning, shipping estimates, or legal business-day requirements. The same tool also includes two additional modes: a recurring event tracker that counts days until the next occurrence of any annual event (like a birthday or anniversary), and an add/subtract mode that lets you add or subtract a specific number of days from any start date to find the resulting calendar date.
When to use a days between dates calculator
This tool is commonly used to calculate the number of days until a deadline, contract expiration, event, or vacation. It is also useful for billing calculations (how many days a service was used), legal date arithmetic (notice periods, statute of limitations), or simply satisfying curiosity about how long ago something happened. HR professionals use it to calculate employee tenure and benefit eligibility periods. Project managers use it to track project duration and milestone spacing.
Event planners use it to count the exact number of days between two dates for scheduling. Teachers use it to calculate homework deadlines and semester lengths. The exclusive/inclusive toggle lets you choose whether to count the start and end dates, giving you full control over the result. The recurring event mode is perfect for counting days until Christmas, a birthday, an anniversary, or any annual celebration — just set the month and day, and the calculator automatically finds the next occurrence and counts the days. All modes save your dates in the browser so they persist across sessions, and the results update instantly as you make changes.
Common mistakes people make
The most common confusion I see is whether "between" includes the end date or not. If a contract says something is due within 30 days of signing, does day 1 start the day you sign (inclusive) or the day after (exclusive)? Lawyers and courts vary on this, and so do different jurisdictions. The calculator's "Include end date" checkbox lets you toggle between the two interpretations so you can match whatever convention your contract uses. Another mistake: assuming every month has 22 business days. A month with a federal holiday and five weekends can have as few as 19 business days, and the calculator's business-day-only mode catches this automatically. Time zones also trip people up — when counting days across time zones, the calculator uses local time, but for precise international deadlines you should be explicit about which time zone you're counting from.
How to use this calculator
- Enter the start date — Select the start month, day, and year using the dropdowns and input. You can use any date from the past or future.
- Enter the end date — Select the end month, day, and year. The end date can be before or after the start date — the calculator always shows a positive result.
- Read the result — The exact difference in days appears immediately, along with the equivalent in weeks, months, and years.
Frequently asked questions
How many days are between January 1 and December 31?
There are 364 days between January 1 and December 31 in the same year (not counting either endpoint), or 365 days if counting both the start and end dates. In a leap year, the full year contains 366 days. The calculator counts either inclusively or exclusively depending on how you define 'between' — toggle the include-endpoints option.
How do I count only business days between two dates?
Business days exclude weekends (Saturday and Sunday) and public holidays. Between two dates 30 calendar days apart, there are roughly 21-22 business days, depending on how many weekends fall in the range. The calculator counts weekdays automatically. For US federal holidays, subtract the number of holidays that fall within your date range.
How many weeks are between two dates?
Divide the number of days between two dates by 7 to get weeks. For example, 91 days ÷ 7 = 13 weeks exactly. For non-divisible results like 100 days, that's 14 weeks and 2 days. The calculator displays the result in days, weeks, months, and years simultaneously so you don't need to convert manually.
How many months and days between two dates?
Calculating months between dates requires accounting for the varying lengths of calendar months. March to October is 7 months regardless of which year. For partial months, count the remaining days after complete months are subtracted. April 15 to October 3 = 5 months and 18 days. The calculator handles all calendar irregularities automatically.
How do I calculate how many days until a future date?
Enter today as the start date and your target date as the end date. The calculator subtracts today's date from the future date to show the exact number of days remaining. For recurring annual dates like birthdays or anniversaries, it finds the next occurrence automatically and shows the countdown in days, weeks, and months.
How many days are in a year?
A standard calendar year has 365 days. A leap year has 366 days and occurs every 4 years, in years divisible by 4 — except century years, which must be divisible by 400. So 2000 was a leap year, 1900 was not. When calculating days across multiple years, the calculator accounts for all leap years in the range automatically.