Calendar days, working days, and date arithmetic
The distinction between calendar days and working days comes up constantly in contracts, project planning, legal notices, and HR. Getting it wrong can mean missing a deadline or miscalculating a delivery window.
Calendar days count every single day — Monday through Sunday, public holidays included. When a lease says "30 days notice," that's 30 calendar days. When a warranty runs for "one year," it runs for 365 (or 366) calendar days.
Working days (also called business days) exclude weekends and, depending on the country, public holidays. A "10 business day" turnaround starting on a Monday ends two full weeks later, skipping the two intervening weekends.
The Working days tab in this calculator handles both, including country-specific public holidays for Canada, the US, UK, Australia, and New Zealand — so you get an accurate count regardless of when the period falls.
The working days calculator includes national public holidays for five countries. Note that many countries also have regional or provincial holidays — this calculator uses national-level holidays only.
| Country | Key holidays included |
|---|---|
| 🇨🇦 Canada | New Year's, Good Friday, Easter Monday, Canada Day, Labour Day, Remembrance Day, Christmas, Boxing Day |
| 🇺🇸 United States | New Year's, MLK Day, Presidents Day, Memorial Day, Independence Day, Labor Day, Veterans Day, Thanksgiving, Christmas |
| 🇬🇧 United Kingdom | New Year's, Good Friday, Easter Monday, Early May bank holiday, Spring bank holiday, Summer bank holiday, Christmas, Boxing Day |
| 🇦🇺 Australia | New Year's, Australia Day, Good Friday, Easter Saturday & Monday, Anzac Day, Queen's Birthday, Christmas, Boxing Day |
| 🇳🇿 New Zealand | New Year's (2 days), Waitangi Day, Good Friday, Easter Monday, Anzac Day, Queen's Birthday, Labour Day, Christmas, Boxing Day |
One of the most common sources of confusion in contracts is whether "days" means calendar days or business days, and whether the trigger date itself counts as day zero or day one.
Most legal systems default to calendar days unless a contract explicitly says otherwise. In many jurisdictions, the day the contract is signed or the notice is given is counted as day zero, and counting begins the following day — so a "30-day notice" given on March 1 expires on March 31, not March 30.
Some contracts — especially in finance, procurement, and employment — specify business days explicitly, which then requires accounting for weekends and local public holidays. A "10 business day" payment term in Canada starting on a Friday will land on a different date than the same term starting on a Monday.
When in doubt about a specific contract, consult a lawyer. This calculator is a planning tool, not legal advice.
This date calculator handles three common date tasks: finding the number of days (or weeks, months, years, hours, or minutes) between any two dates; adding or subtracting a number of days from a start date; and counting working days between dates with country-specific public holidays excluded. Public holidays are calculated using fixed-date and algorithmically determined dates (including Easter) for Canada, the US, UK, Australia, and New Zealand. All calculations run in your browser — no data is sent anywhere.