Counting days sounds simple until deadlines get real
Legal contracts, construction timelines, lease agreements, and loan notice periods all run on day counts — and the difference between calendar days and business days is significant. A 30-day notice delivered on a Friday does not expire 30 business days later; it expires 30 calendar days later, often mid-week. Courts and landlords do not use the same definition, and getting the wrong count can cost you a deposit, a court date, or a contract right.
Weeks and months are deceptively slippery units. A month is not 30 days — it is 28, 29, 30, or 31 depending on where you land. A 6-month contract that starts August 15 ends February 15, which is only 184 days, not 180. This calculator gives you the exact span in days, weeks, and optionally business days so you can anchor to whichever unit your specific deadline requires.
Frequently asked questions
What counts as a business day in date-difference calculations?
Standard business days exclude <strong>Saturdays, Sundays, and federal holidays</strong>. However, what counts as a holiday varies by jurisdiction and industry — US federal holidays differ from state holidays, and banking holidays differ from court holidays. This calculator excludes weekends and the 10 major US federal holidays. If your contract specifies a different holiday schedule, manually adjust the result by the holidays that fall in your range.
Is the start date or end date included in a day count?
This is the most common source of discrepancy between calculators. We use <strong>inclusive start, exclusive end</strong> — the same convention used by most programming languages and legal systems. So from January 1 to January 31 gives 30 days, not 31. If a contract says 'within 30 days of signing' and you signed January 1, your deadline is January 31 — which is the 31st calendar day but the 30th day of elapsed time.
How do I calculate a deadline 90 days from today?
Enter today as the start date and leave the end date blank, then use a date-addition tool — or simply note that 90 days from any date lands three months minus a few days, depending on which months you cross. <strong>Quarter-end deadlines</strong> that run on 90-day windows are particularly tricky in Q1 because of February. For anything legally binding, count the days explicitly rather than approximating by months.
Why do some contracts say 'days' and others say 'business days'?
The distinction is intentional and significant. Consumer protection laws in the US — including the FTC's cooling-off rule — use <strong>calendar days</strong>. Real estate contracts commonly use business days. Employment notice periods vary by state and contract. When a term is not specified, most courts default to calendar days. Always read the contract language exactly; when in doubt, assume calendar days and you will almost never be late.