Date Calculator
Find days between two dates, or add & subtract days from any date — free & instant
About this date calculator
Our date calculator lets you do two types of calculations: find the number of days between any two dates, or add/subtract days from a date to get a future or past date.
Key features
- Dual mode: Date difference and add/subtract days
- Accurate: Full leap year support including century rules
- Wide range: Works for any Gregorian calendar date from 1582
- Private: All calculations run in your browser — nothing is sent to any server
How to calculate days between dates accurately
Manual date counting is error-prone. People forget that February has 28 days in most years, that months have different lengths, and that "30 business days" is very different from "30 calendar days." Our calculator handles all of this automatically.
Why manual date counting fails
Month length errors
February, April, June and others don't have 31 days — manual counts frequently go wrong here.
Calendar vs business days
Most deadlines count working days, but manual counting often includes weekends by mistake.
Leap year mistakes
Forgetting leap years in multi-year calculations can throw off results by a full day.
Common uses
Project deadlines: Know exactly when 45 working days from today falls — without counting on a calendar.
Pregnancy due dates: A standard pregnancy is 280 days from the last menstrual period. Enter the date and get the due date instantly.
Legal deadlines: Courts and contracts often specify deadlines in calendar days. Always verify with a tool rather than counting manually.
Age in days: Want to know how many days old you are? Enter your birthday as the start date and today as the end date.
Free, no signup, instant results.
Frequently asked questions
How accurate is the date difference calculation?
100% accurate. The calculator uses JavaScript's native Date object which correctly handles all leap years, varying month lengths, and century-year rules.
Can I calculate working days only (excluding weekends)?
This calculator counts all calendar days. For business-day-only calculations, use our dedicated business days calculator.
Is there a limit on how many days I can add or subtract?
No. You can add or subtract any positive or negative number of days. The calculator handles large numbers across centuries accurately.
Does it work for historical dates before 1900?
Yes. It works for any date in the Gregorian calendar (after October 1582). Note that different countries adopted the Gregorian calendar at different times.
How do I subtract days from a date?
Switch to the "Add / Subtract Days" tab, enter your base date, and type a negative number (e.g. -30 to go back 30 days). Click Calculate to see the result.