Date Subtraction Calculator
Subtract years, months, weeks and days from a date, or count back a number of business days from a deadline.
Your inputs
Results
Resulting date
Saturday, February 28, 2026
- ISO date
- 2026-02-28
- Day of the week
- Saturday
- Calendar days back
- 31
✓Exact calculation — rounded only for display
What this calculator does
Work backwards from a deadline or event — calendar time or business days.
Formula and method
Calendar: (date − months, clamped) − days; Business: step back skipping weekend days
Worked example
Calculated by this tool with its default inputs:
Inputs
- Start date: 2026-03-31
- Subtract: Calendar years, months, weeks and days
- Years: 0
- Months: 1
- Weeks: 0
- Days: 0
- Weekend days: Saturday & Sunday
Results
- Resulting date: Saturday, February 28, 2026
- ISO date: 2026-02-28
- Day of the week: Saturday
- Calendar days back: 31
How to read the results
Counting back business days is useful for submission deadlines.
Assumptions and limitations
- Date-only arithmetic on the Gregorian calendar; results do not depend on your time zone or daylight-saving changes.
Questions
Does it skip holidays?
Weekend days only; for holidays use the business days calculator with a negative number of days.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 4 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy