Add or subtract days from any date, or calculate the exact difference between two dates. Automatically handles leap years, shows day of week. π No registration Β· Data stays local
Quick:
Click calculate or use quick buttons to see result
π All calculations happen locally in your browser. No data is ever uploaded. Try disconnecting your internet to verify.
β FAQ
Can I use negative numbers for days?
Yes. Enter a negative number to subtract days. For example, -7 means go back 7 days β same result as selecting "Subtract" with 7 days. This gives you flexibility in how you express the direction.
Can I calculate the difference between two dates?
Yes. Click the "Date Difference" tab at the top, select start and end dates, and you'll instantly see the exact number of days, weeks, and months between them. Perfect for project timelines, contract countdowns, and event planning.
Is the calculation accurate for leap years?
Absolutely. The tool uses the browser's native Date object, which correctly handles leap years, varying month lengths, and year boundaries. For example, Feb 29, 2024 (leap year) + 365 days correctly returns Feb 28, 2025, and +366 days returns Mar 1, 2025.
Is my data uploaded to any server?
Never. All calculations happen locally in your browser. Press F12 to open DevTools and check the Network panel β you'll see zero data requests. The tool works perfectly even when you're offline.
What are common use cases?
Project deadline calculation (today + 90 days), contract expiration tracking (signing date + 365 days), event countdowns, shipping ETA estimation, pregnancy due date (LMP + 280 days), shelf life calculation, and more.
Free online date calculator β add or subtract days from any date, and calculate the exact difference between two dates. Automatically handles leap years and varying month lengths. Shows day of week for every result. Perfect for project management deadlines, contract expiration tracking, countdown timers, shipping ETAs, and pregnancy due date calculations. Everything runs locally: Date and Days are processed on your device, never sent to a server with zero data upload.