Date Difference Calculator
Count the calendar days between any two dates and see the result broken into years, months, weeks, and days. The calculator also reports the weekday count and the count after US federal holidays are excluded, so you can compare a calendar span against a working-day span at a glance.
Useful for project spans, gestational-age estimates, anniversary math, contract durations, and the literal “how many days until” question that calendar apps answer poorly. If you only need working-day math (Net 30, SLAs, court filings), use the business days between dates calculator instead.
Worked example: a 14-month consulting contract
A consultant in Austin signs a fixed-fee engagement starting March 1, 2026 and ending May 15, 2027. Plug those dates into the calculator with both Include toggles on and you see 442 calendar days, which decomposes into 1 year, 2 months, 1 week, and 7 days. Of those 442 days, 316 are weekdays. Subtract the US federal holidays that land on a weekday across that span (10 of them) and the working-day count drops to 306. That number drives the realistic consultant-day burn rate, while the 442-day calendar span is what the client's legal team will reference in the renewal clause. The two numbers differ by roughly 30 percent; reading either one in isolation will mislead a budget conversation.
When calendar days are the right frame
Reach for calendar days when the meter runs every day regardless of whether anyone is at a desk. Examples: rent owed per day on a commercial lease, daily interest accrual on overdue invoices (where the late payment statute uses calendar days), insurance policy duration, gestational age, and any count-up-to-an-anniversary calculation. Net 30 is also a calendar-day count under standard US B2B convention. Use business-day math only when the contract or statute explicitly says "business days" or "working days".
How leap years and DST change the answer
Any calendar-day span that crosses Feb 29 in a leap year picks up one extra day. The next leap day is Feb 29, 2028. A range from Feb 1, 2028 to Mar 1, 2028 is 29 days; the same range a year later is 28 days. Daylight saving time does not change the count: the calculator works in pure calendar dates and ignores the spring-forward and fall-back hour shifts entirely. If you need hour-level math across DST transitions, use the working hours calculator, which respects daily start and end times rather than counting whole days.
The Include start and Include end toggles
Both toggles default to a sensible state (start off, end on), which matches the behavior of most calendar apps and contract counting conventions. Turn Include start on when the start date itself is a billable day, an occupancy day, or a day-one-of-coverage situation. Turn Include end off when you are measuring an exclusive interval such as a hotel checkout date that does not count as a paid night. The number above the breakdown updates instantly as you toggle, so you can compare frames without recalculating.
For informational purposes only
This calculator provides general estimates based on business day counting rules. It does not constitute legal advice. Deadlines in legal, regulatory, or contractual matters may be subject to jurisdiction-specific rules, court orders, or statutory exceptions. Always verify critical deadlines with a qualified professional.