Date Calculator
Date calculator: count days between two dates, add or subtract days from a date, and count down to a date. Runs in your browser, no data stored.
Thursday, June 25, 2026 → Thursday, June 25, 2026 = 0 days (excluding both dates).
This is a general date calculator. It is not a substitute for checking an official deadline in source documents or with a qualified professional. For legal, tax, insurance, immigration, visa, parental-leave, sick-leave, or academic-registration dates, check an official source or consult a professional. The calculation runs in your browser only; no value is sent to a server or stored.
A free date calculator that runs entirely in your browser. Three modes: (1) Difference between two dates: find the number of days between dates, with the total shown as days, a weeks-and-days breakdown, and a calendar breakdown into years, months, and days, plus an option to count both endpoints. (2) Add or subtract days from a date: add days to a date or subtract days from a date and get the resulting date and its day of the week. (3) Countdown to a date: see how many days until a date, or how many days have passed since it, along with the weekday it falls on. All calculations work on whole dates only (no hours) and use UTC internally to avoid time bugs around daylight saving or time-zone offsets. This is a general date calculator, not a substitute for advice on legal, tax, insurance, immigration, school, or medical dates. For an official, legally or administratively binding date, check the authoritative source or consult a qualified professional. Your data stays with you: the dates, the day counts, and the results are never stored and never sent to any server. Refreshing the page resets everything. Last updated: May 2026.
How to use this tool
- 01Choose a modeThree modes: "Difference between two dates", "Add / subtract days", and "Countdown to a date". Each does a different job, and you can switch between them without losing the other dates on the page.
- 02Enter datesDates use the yyyy-mm-dd format (for example 2026-05-30). On mobile, the device shows a graphical date picker. The supported range is 1900 to 2200, which covers any realistic planning.
- 03Read the full resultIn difference mode: total days, weeks + days, and years/months/days by calendar. In add/subtract mode: the resulting date plus its day of the week. In countdown mode: days left or days passed, plus the day of the week of the target date.
- 04Copy the resultThe "Copy result" button copies a short summary line for the current mode that you can paste anywhere. There is no print or download button.
When is this useful?
- Planning an exam or projectCheck how many days are left until the submission day. Switch to "Countdown" and enter the target date. You see how much time is left and which day of the week the target falls on.
- Age difference between two peopleEnter two birth dates and get the difference in days, weeks, and a years-months-days calendar breakdown. This tool is general. For a full age and next-birthday calculation, there is a dedicated "age calculator".
- Planning a tripCheck how many days fall between departure and return to plan insurance, registrations, or a schedule. Difference mode also shows the span in each unit (days, weeks + days, months).
- Finding a date after a waiting periodEnter a start date and a number of days (for example 90 days after a submission) and get the exact date that follows. The tool is for orientation only. It does not replace checking an official deadline.
- Counting how long since an eventEnter a past event date in "Countdown" mode and get the number of days that have passed. Useful for tracking anniversaries, a memorial day, or personal dates.
Examples
- Difference between two datesFrom 2026-01-01 to 2026-12-31 = 364 days = 52 full weeks plus 0 days. Including both dates: 365 days. By calendar: 0 years, 11 months, and 30 days.
- Adding days to a date2026-05-30 + 100 days = 2026-09-07, a Monday.
- Subtracting days from a date2026-05-30 minus 14 days = 2026-05-16, a Saturday.
- Counting down to a dateIf today is 2026-05-30 and the target is 2026-12-31, 215 days are left. If the target is today itself, it shows "Today!". If the target is in the past, it shows how many days have passed, not an error.
- Leap year and February 292024 was a leap year. 2024-02-28 + 1 day = 2024-02-29. 2025 is not a leap year: 2024-02-29 + 365 days = 2025-02-28. The tool handles the jumps correctly.
Tips for a better result
- Including or excluding both datesThe "plain" difference between June 2 and June 5 is 3 days (2 → 3 → 4 → 5, counting the transitions). If you want to count both dates themselves (for example "how many days I attended a conference" that ran June 2-5), that is 4 days. Use the "count both dates" toggle to match your context.
- A "rounded" month versus a real monthThe tool shows a calendar breakdown: years-months-days that fit the dates exactly. It does not show "roughly how many months" because a calendar month is 28 to 31 days. For calculations that need a uniform unit (for example a monthly index adjustment), use the day count only or a dedicated tool.
- Time zones and daylight savingThe tool works on dates only, with no hours, and uses UTC internally. This ensures that a daylight-saving change or a time difference between countries cannot push the result off by a day. "Today" is determined by your local date.
- Your data stays with youThe dates you enter, the number of days you type, and the results all stay on your device. There is no sending to a server, no storage, and no tracking of the values. Refreshing the page resets everything.
Finding the weekday of a future or past date
Both the add/subtract mode and the countdown mode tell you the day of the week of the date in question. Add days to a date to see what weekday a future date lands on, subtract days to check the weekday of a past date, or open a countdown to a date to learn which day of the week an upcoming event falls on. This is handy when you want to know whether a deadline that is a set number of days away lands on a weekend, or which weekday a date a few months out will be.
How the calculation works
Each date is converted internally to a number of milliseconds from the start of the day in the UTC time zone. The operations (subtracting two dates, adding days, the difference between a target and "today") are done with simple millisecond arithmetic, and the conversion back to a date uses UTC values. The reason: in a local time zone, a simple add operation around a daylight-saving change can create a one-day error, because the local "midnight" shifts by a few hours twice a year. With UTC, a day is always exactly 86,400,000 ms. The calendar breakdown into years/months/days uses a "walk" method: the day-of-month difference comes first, and if it is negative the tool borrows a day from the previous month of the end date, then the month difference, and if it is negative it borrows from the previous year.
What the tool does not do
The tool is not a substitute for an official source for a legal, tax, insurance, immigration, parental-leave, sick-leave, visa, passport, school-enrollment, or academic-registration date. It does not calculate severance pay, does not calculate gestational age, is not an estimated due date for a baby, and is not a business-days calculator (for a tool that accounts for weekends and Israeli holidays, a dedicated tool is needed). It is also not a reminder or a calendar: if you close the page, the dates are erased from memory. For active tracking of target dates, use a personal calendar.
Accuracy and leap years
The tool handles leap years correctly (a year divisible by 4 and not by 100, or divisible by 400). February 29 is valid only in leap years; entering a date like 2025-02-29 is treated as invalid. Month boundaries and year boundaries are handled properly for both adding and subtracting days.
Privacy
Everything happens in your browser. The dates you enter, the day counts, and the results: no value is saved to localStorage, sent to a server, or passed to analytics. Refreshing the page resets everything. No signup, no account, and no tracking.
Frequently asked questions
What is a date calculator?
A tool that does three different calculations on dates: the difference in days between two dates, adding or subtracting days from a date, and counting down to a future date or counting the days since a past date.
How do I find the number of days between two dates?
Choose "Difference between two dates", enter a start date and an end date, and read the total days between dates. The same result is also shown as weeks plus days and as a calendar breakdown into years, months, and days, so this works as a full date difference calculator for any two dates.
How do I add days to a date?
Choose "Add / subtract days", enter the start date, type the number of days to add, and the tool returns the resulting date along with its day of the week. Add days to a date for deadlines, delivery windows, or a date a fixed number of days in the future.
How do I subtract days from a date?
Use the same "Add / subtract days" mode and subtract days from a date instead of adding. Enter the date and the number of days to go back, and the tool shows the earlier date and which weekday it falls on, crossing month and year boundaries correctly.
How many days until a specific date?
Choose "Countdown to a date" and enter the target date to see how many days until that date, counted from today. The countdown also shows the weekday of the target date. If the date is today it shows "Today!", and if the date has already passed it shows the days since instead of an error.
What does "count both dates" do?
The "count both dates" toggle makes the difference inclusive of both endpoints. Without it, June 2 to June 5 is 3 days (the span between them). With it turned on, the same range is 4 days, because the start day and the end day are both counted, which matches how you would count a conference or a stay that runs from June 2 to June 5.
How does the difference calculation work?
The tool measures the difference in whole days between the two dates. One option counts both dates (for example a 4-day conference from June 2 to 5), and another option excludes them (3 days of span, suited to "how much time has passed" calculations).
What is the difference between a date calculator and an age calculator?
An age calculator is dedicated to the question "how old am I?", including the next birthday and the age on a target day. A date calculator is more general. It works on any two dates, not just a birthday, and also does add/subtract of days and a countdown.
Does the tool account for weekends and holidays?
No. The tool counts calendar days. Every day is one day, including Saturday and holidays. For a business-days calculation (five days a week, excluding Israeli holidays), a separate tool is needed.
How does the tool handle leap years?
2024 is a leap year, so 2024-02-29 is a valid date; 2025 is not a leap year, so 2025-02-29 is treated as invalid. When adding and subtracting days, the tool crosses February 29 without bugs.
What happens if the target date is already in the past?
In "Countdown" mode: if the target is today itself, it shows "Today!". If the target is in the past, it shows the number of days that have passed since, not an error. In "Difference between two dates" mode: if the end date is earlier than the start date, the count is backward (a negative difference) and the absolute value is shown as well.
Is the tool suitable for a legal deadline, a tax filing, or a visa validity?
No. The tool is a general date calculator only. It is not a substitute for checking an official deadline in source documents or with a qualified professional. For legal, tax, insurance, immigration, visa, passport, or academic-registration dates, check an official source or consult a professional in the relevant field.
What range is supported?
The tool supports dates between 1900 and 2200. That is enough for any practical planning: historical birth dates, future events, and long-term projects.
What happens if I enter a date in an invalid format?
An explanation is shown ("Enter a date in a valid format yyyy-mm-dd") and no result is displayed. A date outside the supported range is also flagged with an explanation.
Is my data stored or sent anywhere?
No. All calculation happens in your browser. The dates, day counts, and results are not saved to localStorage, not sent to a server, and not passed to analytics.
Is the tool free?
Yes. The tool is free, with no signup and no usage limit.
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