Date Add/Subtract Calculator
Add or subtract days, weeks, months, or years from any date.
Quick Presets
Result Date
Day of Week
ISO Format
Days from Today
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Frequently Asked Questions
How do I add months to a date when month lengths differ?
When adding months, if the resulting day exceeds the new month's length, it rolls to the last day of that month. For example, adding 1 month to January 31 gives February 28 (or 29 in a leap year). This is a standard convention used by most date calculation libraries.
What is the difference between adding calendar days and business days?
Adding 10 calendar days to a Monday gives the Thursday of the following week (counting all days). Adding 10 business days to a Monday gives the Monday two weeks later (skipping weekends). Legal and business contexts typically specify which method to use.
How do leap years affect date calculations?
A leap year adds February 29, which affects day counts crossing February. Leap years occur every 4 years, except centuries not divisible by 400. So 2024 and 2028 are leap years, but 1900 was not (2000 was). This calculator automatically handles leap years.