BCBetter Calculators

Date Subtract Calculator

Subtract a number of days, weeks, or months from a date to find an earlier date.

🧮

Enter your values and click Calculate

How It Works

The start date is first validated with a UTC round-trip check that rejects impossible dates like February 31. Weeks are converted to days (weeks × 7) and added to the day subtraction total. Months are subtracted by passing a negative month offset to JavaScript's Date.UTC() constructor: new Date(Date.UTC(year, month − subtractMonths, day − totalDays)). The Date constructor automatically handles overflow in both directions — subtracting past month 0 rolls back the year, and subtracting past day 1 rolls back the month. The result is formatted as YYYY-MM-DD (ISO 8601) and a human-readable total day count is calculated for reference.

Examples

Subtract 30 days from June 15, 2025
Find a date 30 days before a deadline.
Result: Result: 2025-05-16.
Subtract 3 months and 2 weeks from December 1, 2025
Working backwards for a project start date.
Result: Result: 2025-08-18.
Subtract 6 months from March 31, 2026
Lease notice period calculation crossing a year.
Result: Result: 2025-09-30 (month-end clamped to September's last day).

Frequently Asked Questions

What happens when subtracting months crosses a year boundary?
The calculator handles this automatically — subtracting 3 months from February 2025 correctly returns November 2024. JavaScript's Date constructor manages year rollover when the month index goes below 0.
Can I subtract just weeks or just months?
Yes — leave unused fields at 0. You can subtract any combination of days, weeks, and months independently, and the calculator combines them into a single correct result date.
What if subtracting months produces an invalid day, like February 31?
JavaScript's Date constructor automatically clamps invalid dates to the last valid day of the month. Subtracting one month from March 31 produces February 28 (or 29 in a leap year) rather than an error.

Related Calculators

life✨

Time Duration

Calculate the number of days and weeks between two dates.

Calculate →
life✨

Work Hours

Calculate how many hours you worked in a day after accounting for breaks.

Calculate →
life✨

Age Difference

Calculate the age difference between two birthdays in years, months, and days.

Calculate →