Add Days Calculator
Perfect for project scheduling, medication plans, event countdowns, or backdating historical research.
Example: +45 for 45 days ahead, -10 for 10 days prior.
Start date: Tuesday, November 25, 2025
Resulting date: Thursday, December 25, 2025
Total days: 30 (4.29 weeks • 0.99 months • 0.08 years)
Difference from today: 30 day(s) remaining
How to Use This Calculator
Provide the start date
Pick the anchor date for your calculation.
Enter day offset
Use positive numbers to look ahead and negative numbers to go back in time.
Record the results
Add the target date to your planning documents, calendar, or workflow tools.
Formula
Target Date = Start Date + N days
Weeks = N ÷ 7 • Months ≈ N ÷ 30.4375 • Years ≈ N ÷ 365.25
Example: Start 2025-11-09 + 123 days → 2026-03-12 (Thursday).
Planning Ideas
- Track contract notice periods or legal lookbacks.
- Schedule project sprints, training cycles, or residency periods.
- Convert medication instructions (e.g., 21 days) into calendar dates.
- Plan content schedules or countdown campaigns.
Frequently Asked Questions
Can I add partial days?
This tool works in whole days. For hours/minutes precision, use the Add Time Calculator or Adding Hours Calculator.
Does it handle leap years?
Yes—adding days uses native calendar math, so Feb 29 is included automatically when applicable.
What if I need business days?
Use the Business Days Calculator to exclude weekends and holidays.
Can I calculate multiple milestones?
Yes—log each result or export to spreadsheets to build complex schedules.