Days Between
Select two dates to see the difference
Quick Date Info
Select a date above to see its details.
This date calculator answers the two questions that come up constantly in planning: how many days lie between two dates, and what date you land on after adding or subtracting days. It handles leap years, uneven month lengths, and year rollovers, so planners get a reliable answer in seconds.
Why Date Arithmetic Is Trickier Than It Looks
Months have 28, 30, or 31 days, and February gains a day in leap years — which follow the rule “divisible by 4, except centuries, unless divisible by 400,” so 2000 was a leap year but 1900 was not. Adding 30 days to late January lands on a different date depending on the year, and mental math breaks across year boundaries. A calculator encoding Gregorian rules removes the off-by-one errors that slip into contracts, plans, and countdowns.
How to Use
- Choose a mode: “Days between” two dates, or “Add / Subtract” days from a base date.
- In Days Between mode, pick start and end dates — the result shows total days plus week, month, and year equivalents.
- In Add / Subtract mode, enter a base date and a number of days; use a negative number to go back in time.
- Check the extras: day of the week, weekend flag, and leap year status.
Features
- Two modes: date difference and date offset
- Results in days, weeks, months, and years
- Day-of-week and weekend indicators
- Full leap year handling under Gregorian rules
- Negative offsets for counting backwards
- Runs entirely in your browser
Use Cases
Project managers compute days left before a milestone. HR and legal teams check notice periods and contract durations. Event planners count down to launches, expecting parents track pregnancy weeks, and finance teams check interest accrual periods.
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Frequently Asked Questions
How is the "months between" value calculated?
The months calculation compares the month and year components of the two dates. For example, January 15 to March 10 is approximately 1 month and 23 days, so the tool reports 1 month. The calculation accounts for varying month lengths.
Can I subtract days to find a past date?
Yes, in Add / Subtract mode, enter a negative number (e.g., -30) to go backwards in time. The tool automatically handles month and year rollovers correctly.
Does it account for leap years?
Yes, the date calculator fully accounts for leap years. February has 29 days in leap years, and the tool correctly identifies whether a given year is a leap year using the standard Gregorian calendar rule.