Count the days between two dates, or add and subtract days, weeks, months, and years from any date. Includes business-day counts, weekend counts, and a full calendar breakdown.
To count days between dates manually, add up the days remaining in the start month, the full months in between, and the days elapsed in the end month. For example, from July 4 to December 25: July has 27 days left (31 − 4), then August (31) + September (30) + October (31) + November (30) = 122 days, plus 25 days of December — 27 + 122 + 25 = 174 days. The calculator does exactly this, including leap-year February handling, so you don't have to track month lengths yourself.
Common waiting periods — return windows, probation periods, notice periods, and payment terms — are usually stated in days. Here is how the most common spans convert:
| Calendar days | Weeks + days | Approx. months | Business days (Mon–Fri) |
|---|---|---|---|
| 30 days | 4 weeks 2 days | ≈ 1 month | 21–22 |
| 45 days | 6 weeks 3 days | ≈ 1.5 months | 31–33 |
| 60 days | 8 weeks 4 days | ≈ 2 months | 42–44 |
| 90 days | 12 weeks 6 days | ≈ 3 months | 64–66 |
| 120 days | 17 weeks 1 day | ≈ 4 months | 85–86 |
| 180 days | 25 weeks 5 days | ≈ 6 months | 128–130 |
| 365 days | 52 weeks 1 day | 12 months | 260–261 |
Business-day counts are ranges because they depend on which weekday the span starts; public holidays are not subtracted.
Contracts and shipping estimates often mix the two conventions, and the difference is large: 10 business days is two full weeks (14 calendar days), and a “90-day” probation period contains only about 65 working days. When a deadline matters — visa windows, return policies, court filings, loan rate locks — first check whether the document says calendar days or business days, then use the matching count above. If the deadline lands on a weekend, most (but not all) rules roll it to the next business day.
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