How to use this date calculator
Add or subtract: pick a start date (defaults to today), choose add or subtract, enter a number, and choose days, business days, weeks or months. The result shows the full date with its weekday.
Days between dates: switch to the second tab, enter two dates, and see the difference in days and weeks, with and without the end date included.
Looking for a specific count? Jump straight to 30 days from today, 45 days, 60 days, 90 days or 180 days.
Common uses
- Payment terms — “Net 30” means the invoice is due 30 days after the invoice date.
- Return windows — many retailers allow 30, 60 or 90 days.
- Notice periods — a 30-day notice on a lease, or a 90-day probation period at a new job.
- Legal deadlines — filing periods are often expressed in days, and sometimes specifically in business days.
- Medical — prescription refills, follow-up appointments and pregnancy dates are all counted in days or weeks.
- Planning — countdowns to a trip, a wedding, an exam or a project milestone.
Calendar days vs business days
Thirty calendar days from a Friday is a Sunday four weeks later. Thirty business days from the same Friday is six weeks later, because weekends don’t count. When a contract or regulation doesn’t specify, calendar days are the usual default, but check — the difference can be more than a week.
Quick reference from today
| Days | Roughly |
|---|---|
| 7 | 1 week |
| 14 | 2 weeks |
| 30 | about 1 month |
| 45 | about 6½ weeks |
| 60 | about 2 months |
| 90 | about 3 months (a quarter) |
| 180 | about 6 months |
| 365 | 1 year |
Months vary between 28 and 31 days, so “30 days” and “one month” rarely land on the same date. When a deadline says “one month”, use the months option; when it says “30 days”, use days.
Frequently asked questions
Does the count include today?
No. "1 day from today" is tomorrow. If a deadline says "within 30 days including today", enter 29.
What counts as a business day?
Monday to Friday. Public holidays are not skipped because they vary by country and state; check the result against a holiday calendar for legal deadlines.
How are months added?
The same day of the next month. If that day doesn't exist (January 31 + 1 month), the result rolls forward into the following month — the behaviour most calendar software uses.
How is "days between dates" counted?
As the number of midnights crossed, so January 1 to January 2 is 1 day. If you need to include both the start and end dates (common for rental or billing periods), use the "includes end date" figure.
Last updated August 26, 2026.