Calculate days between dates and add or subtract days from a date.
Dates matter in almost every area of life — contracts, deadlines, pregnancies, anniversaries, legal notices, and financial planning all revolve around specific dates and durations. Our Date Calculator lets you find the exact number of days between any two dates, add or subtract days from a given date, or find out what day of the week any date falls on.
It's the tool you reach for when your lease says "90 days notice," your doctor says "come back in 6 weeks," or your project manager says "how many working days until the deadline?"
Enter two dates to find the difference in days, weeks, months, and years. Or enter a start date and a number of days to add or subtract, and the calculator returns the resulting date including the day of the week. Business day calculations exclude weekends and optionally exclude US federal holidays.
Scenario: You signed a commercial lease on January 10, 2026, and your contract requires 90-day written notice before vacating.
Notice deadline = January 10 + 90 days = April 10, 2026
Day of week: Friday
If you plan to leave August 1, 2026, you must send notice by:
Business day version (excluding weekends): your notice must arrive by Friday, May 1, 2026 — the last business day before the 90-day cutoff.
The Date Calculator catches this nuance instantly so you don't miss a critical deadline.