Date Difference Calculator
Enter a start and end date below, and this days between dates calculator outputs the exact span in days, weeks, months, and years.
About
About Date Difference Calculator
Counting days between two calendar dates by hand is harder than it sounds, since months run different lengths and roughly every fourth year adds an extra day in February. A date difference calculator handles that irregularity automatically, and this days between dates calculator breaks the result down into days, weeks, months, and years all at once.
The leap year rule itself has a quirky exception most people have never actually needed to know: a year is a leap year if divisible by 4, except century years, which only count as leap years if also divisible by 400. That's why 2000 was a leap year but 1900 wasn't, a rule obscure enough that manual date math gets it wrong more often than people realize.
Whether to count a date range inclusively or exclusively, does the end date itself count as a full day, actually matters for contracts, legal deadlines, and project timelines, where an off-by-one error on a filing deadline is a real problem, not just an academic nitpick.
Pick your start and end dates from the calendar pickers, and the duration calculates immediately, shown simultaneously in total days, weeks, months, and years, no manual equation needed.
This handles date ranges spanning decades or centuries just as cleanly as a short gap, which makes it equally useful for a project deadline next month or a genealogical research question spanning a century. Your dates and the context behind them stay entirely private, calculated locally.
FAQ
Frequently asked questions
How does the calculator handle leap years correctly?
It automatically applies the actual leap year rule, divisible by 4, except century years unless also divisible by 400, factoring in every extra February 29th that falls within your date range.
Does the result include both the start and end date?
Standard output measures total elapsed time between the two dates. Depending on what you're calculating for, like a legal deadline, you may need to decide separately whether the end date itself should count as a full additional day.
Can I calculate a date range far in the past or future?
Yes, the underlying calendar math handles date ranges spanning decades or even centuries without any accuracy loss, useful for historical research as much as everyday scheduling.
How many weeks are actually in a year?
A standard year has 52 full weeks plus one extra day. A leap year has 52 full weeks plus two extra days, both of which the calculator accounts for precisely rather than rounding.
Is this suitable for business project planning, not just personal use?
Yes, it's fully free for either use, with no account or sign-up required regardless of context.
Are the dates I calculate logged anywhere?
No, every calculation runs locally through client-side JavaScript. Dates you enter are never stored or transmitted to a server.
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