Date Calculator
Three tools in one — calculate days between two dates, add or subtract days from a date, and find upcoming countdowns.
Days Between Two Dates
Add or Subtract Days from a Date
Countdown to a Date
When to Use a Date Calculator
Date calculations come up constantly in daily life and work — calculating project deadlines, finding out how many business days are left in a contract period, figuring out when a 30-day return window expires, planning events, or determining exactly how long ago something happened. This tool handles all three core date math scenarios instantly.
Business Days vs Calendar Days
Calendar days include all 7 days of the week. Business days (also called working days) exclude Saturdays and Sundays — typically used for contracts, legal deadlines, shipping estimates, and financial transactions. A 10 business day period spans exactly 2 calendar weeks, while 30 calendar days contains about 21 business days.
ISO Week Numbers and Date Arithmetic
Months have varying numbers of days (28–31), making simple division imprecise. This calculator uses exact millisecond arithmetic between dates for precise day counts, with floor division for complete weeks. Leap years are handled automatically — 2024 and 2028 are leap years with 366 days.