How does the Add or Subtract Days from Date work?

For days: add/subtract directly from the date Then: For weeks: multiply by 7 then add/subtract days Then: For months: adjust the month field and handle month-end overflow Then: JavaScript Date handles leap years automatically.

Can you give an example of how to use the Add or Subtract Days from Date?

Example: Input Jan 15 + 90 days gives a result of April 15 (or 16 in leap year).

Is the Add or Subtract Days from Date free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Add or Subtract Days from Date?

Our Add or Subtract Days from Date uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

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Add or Subtract Days from Date

Start Date

Amount

Unit

An add or subtract dates calculator computes a new date by adding or subtracting a specified number of days, weeks, or months from a starting date. Used for deadlines, scheduling, and date planning.

Symbol	Name	Unit	Description
start	Start date	date	Base date (YYYY-MM-DD)
days	Days to add/subtract	days	Positive = future, negative = past
result	Result date	date	The calculated date

Period	Days to Add	Example
1 week	7
2 weeks	14
1 month	28–31	Varies by month
Quarter	90–92	Approx 3 months
Half year	181–184	Approx 6 months
1 year	365 or 366	Leap year check

References

›ISO 8601 date arithmetic

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Add or Subtract Days from Date

Add or Subtract Days from Date

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Common Date Addition Reference

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Add or Subtract Days from Date