Date Calculator
Days between two dates, or add and subtract days from a date.
Find the exact number of days between two dates — with weeks, months, and years too — or switch modes to add or subtract days from a date and see the resulting day of the week.
Calculations are calendar-correct, accounting for leap years and varying month lengths, and use your local time so there's no timezone drift.
100% freeNo sign-up No data leaves your browserPrivacy
Formula
Days between dates
|end − start| ÷ 1 day
The difference between two dates, counted in whole days. Weeks, months, and years are derived from the day count.
Add or subtract days
start date ± number of days
Shift a date forward (positive) or backward (negative) by a number of days to get a new calendar date.
How to use the date calculator
- 1Choose “Days between dates” or “Add / subtract days”.
- 2Pick your date(s) — or enter a number of days to add (or a negative number to subtract).
- 3Read the day count (or the resulting date and weekday); copy or share it.
Examples
| Example | Input | Result |
|---|---|---|
| Full year | Jan 1 → Dec 31, 2023 | 364 days |
| Across a year | Jan 1 2023 → Jan 1 2024 | 365 days |
| Add days | Jan 15 2024 + 30 | Feb 14, 2024 |
How to calculate days between dates
Subtract the earlier date from the later one and count the whole days in between. This calculator also expresses that span in approximate weeks, months, and years — useful for deadlines, anniversaries, due dates, and project timelines. The day count itself is exact; months and years are approximate because they vary in length.
Adding and subtracting days
To find a date a set number of days in the future, add that many days to your start date; to go into the past, subtract. The calculator rolls across month and year boundaries correctly, so adding 30 days to January 15 lands on February 14, and the result shows the day of the week.
Leap years and accuracy
Leap years (every four years, with the usual century exceptions) add a day to February, and this calculator accounts for them automatically because it works on real calendar dates. It also uses local-time date handling, so results don't shift by a day across timezones.
Frequently asked questions
How many days are between two dates?
Subtract the earlier date from the later one. This calculator counts the exact whole days and also shows the span in weeks, months, and years.
How do I add days to a date?
Switch to “Add / subtract days”, pick a start date, and enter the number of days (use a negative number to subtract). The resulting date and weekday are shown.
Does it include both the start and end date?
The day count is the difference between the two dates, so it counts the nights between them — e.g. Jan 1 to Jan 2 is 1 day.
How are months and years calculated?
From the exact day count, using average lengths (about 30.44 days per month, 365.25 per year), so they're close approximations rather than calendar-exact.
Embed this calculator
Add the Date Calculator to your own website — free. Copy and paste this snippet:
<iframe src="https://numvella.com/embed/date-calculator" width="100%" height="460" style="border:1px solid #e2e8f0;border-radius:12px" title="Date Calculator — Numvella" loading="lazy"></iframe>