Find days between two dates, or add and subtract days from any date.
To count days between dates, subtract the start date from the end date. A standard year has 365 days (366 in a leap year). A year has 52 weeks plus 1 or 2 days. Business days exclude Saturdays and Sundays, reducing a 30-day period to about 22 business days.
Computers store dates as numbers — specifically, as the count of days since a reference point (usually January 1, 1970 for Unix systems, or January 1, 1900 for Excel). This means finding the gap between two dates is as simple as subtraction. January 15, 2026 minus January 1, 2026 = 14 days.
Business days (also called working days) exclude weekends. A 30-day period typically contains about 21–22 business days. The exact number depends on where the weekends fall. Public holidays vary by country, state, and employer — this calculator counts weekdays only and does not exclude public holidays.
Project deadlines, contract periods, shipping and delivery windows, payment due dates, loan terms, lease agreements, and age verification all require precise date math. The add/subtract mode is useful for finding a date a fixed number of days in the future or past — for example, "what date is 90 days from today?"