Date & Time calculator
Add Days Calculator - Add or Subtract Calendar Days
Add or subtract a number of calendar days from a start date and see the target date and weekday.
FormulaTarget date = start date + number of calendar days
Formula
Add days formula
This adds calendar days, not business days. Confirm deadlines that depend on holidays, local rules, or timezones.
Target date = start date + number of calendar days
Adding 45 days to 2026-07-14 gives 2026-08-28.
FAQ7 common questions for this calculator.
FAQs
Can I subtract days?+
Yes. Enter a negative number of days to count backward.
Does this skip weekends?+
No. It adds calendar days. Use the Business Days Calculator for weekday-only counts.
Does the start date count as day one?+
No. Adding 1 day moves to the next calendar date. Use Day Counter for inclusive range counting.
How does the Add Days Calculator calculate the result?+
For the Add Days Calculator, it uses the Add days formula: Target date = start date + number of calendar days. Adding 45 days to 2026-07-14 gives 2026-08-28.
What information do I need to use the Add Days Calculator?+
For the Add Days Calculator, enter a start date and see the target date and weekday. Keep the units consistent with the calculator fields and compare your setup with the worked example on the page.
How accurate is the Add Days Calculator?+
Add Days Calculator is accurate for the values and assumptions entered on this page. It uses the Add days formula. Recheck the inputs before relying on the estimate.
What should I check before using the Add Days Calculator result?+
For the Add Days Calculator, check a start date and see the target date and weekday, date format, timezone, daylight-saving changes, inclusive or exclusive endpoints, and whether weekends or holidays should count.
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Date & Time guide
How to use the Add Days Calculator
Add or subtract a number of calendar days from a start date and see the target date and weekday. The page also explains the add days formula and shows a practical example: Adding 45 days to 2026-07-14 gives 2026-08-28.
- 1
Enter your details
Enter a start date and see the target date and weekday, then complete any other fields shown in the calculator.
- 2
Check the calculation
Review the result alongside the add days formula: Target date = start date + number of calendar days.
- 3
Compare scenarios
Change one or more inputs to see how they affect the add Days Calculator result before you use the estimate.