How to Calculate Add Days to Date

What is Add Days to Date?

Date addition/subtraction calculates the resulting date after adding or removing days, automatically handling month boundaries, varying month lengths, and leap years.

Formula

Result date = Start date + n days | Leap year every 4 years except centuries (divisible by 400)

n: Number of days (days)
d_start: Start date (YYYY-MM-DD)

Step-by-Step Guide

1Add days to get future date; subtract to get past date
2Leap years add February 29 every 4 years (with century exceptions)
3Business day calculators exclude weekends and public holidays
4ISO 8601 format (YYYY-MM-DD) avoids ambiguity

Worked Examples

Input

15 February + 14 days

Result

1 March (or 29 February in a leap year)

Frequently Asked Questions

What is Add Days?

Date addition/subtraction calculates the resulting date after adding or removing days, automatically handling month boundaries, varying month lengths, and leap years. Use this calculator for accurate, instant results.

How accurate is the Add Days calculator?

The calculator uses the standard published formula for add days. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Add Days calculator use?

This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Add Days calculator use?

The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.

Ready to calculate? Try the free Add Days to Date Calculator

Try it yourself →