About Date Calculator
Compare dates or add days, weeks and business days with your own holidays.
Calculate calendar intervals without daylight-saving shifts. Business days are Monday through Friday, excluding the holiday dates you enter. The starting date is excluded and the ending date is included.
How to use it
- Choose difference or addition and enter the starting date.
- Enter the ending date or an amount; negative amounts subtract.
- For business days, list holidays as YYYY-MM-DD, one per line.
Common use cases
- Plan delivery windows, study periods and project milestones using an explicit holiday calendar.
Worked example
Friday 2026-09-04 plus one business day is Monday 2026-09-07, or Tuesday if Monday is entered as a holiday.
Limitations and responsible use
- No national holidays are assumed. Dates range from year 0001 to 9999; additions are limited to 100,000 units in either direction. This is a calendar calculation, not a jurisdiction-specific deadline rule.
Frequently asked questions
Does the first date count?
No. Equal dates have a difference of zero. Adding zero returns the starting date, even on a weekend.