Calculating Days Between Dates
How to count the days between two dates and add or subtract days for deadlines and due dates — with the leap-year and month-length details handled for you.
Date math comes up constantly — a project deadline 45 working days out, how long until a trip, the return-by date on a rental. Doing it in your head is error-prone. This guide covers the two most common date calculations and the traps to avoid.
Days Between Two Dates
Find how long it is from one date to another.
Example
This is a sample result, not your calculation. Enter your own values to replace it.
Enter a start date and an end date to see how long it is between them.
Difference
In other units
- Years, months, days
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- Total days
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- Weeks and days
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- Business days
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The same span in other time units
- Seconds
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- Minutes
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- Hours
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- Days
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- Weeks and days
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- Of a common year (365 days)
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Check your dates
Enter a start date and an end date.
Add to or Subtract from a Date
Move a date forward or back by years, months, weeks and days.
Example
This is a sample result, not your calculation. Enter your own values to replace it.
Enter a start date and how much time to add or subtract.
Resulting date
How it was reached
- From
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- Amount
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Check your entries
Enter a start date and how much to add or subtract.
Counting days between two dates
To find the gap between two dates, you need to account for the different lengths of months and any leap days in between. The calculator above counts every actual calendar day, then also expresses the span in years, months, days and weeks — so you can read it however you need.
A common question: do you count both endpoints? For “days between,” it’s usually the difference (the end date minus the start date). If you’re counting inclusive days — like nights on a trip plus one — add one to the result.
Adding and subtracting days
Deadlines are the classic case: “60 days from today.” Rather than counting on a calendar, set a start date, choose add or subtract, and enter the number of days. Adding 90 days to January 1, 2024 lands on March 31, 2024 — and because 2024 is a leap year, February’s extra day is already accounted for.
Watch out for these
- Leap years — every four years February has 29 days, which shifts every later calculation.
- Business days vs. calendar days — contracts often mean working days; this tool counts calendar days.
- Time zones — a date can differ by a day across zones; stick to one reference point.
Related tools
For someone’s age specifically, the age calculator breaks a duration into years, months and days from a birth date. For everything else — durations and deadline math — the date calculator has you covered.