Date Add / Subtract Calculator
Add or subtract days, weeks, months and years to any date, with the resulting weekday.
Last updated: August 2026
Use YYYY-MM-DD.
New date
2026-09-09
Day of week
Wednesday
Days changed
30 days
Added
2026-08-10 is a Monday. Adding 30 days gives 2026-09-09 — a Wednesday.
How it works
Date ± n units. Months/years clamp the day to the last valid day of the target month.
Example: 10 Aug 2026 + 30 days = 9 Sep 2026 (Tuesday).
Frequently Asked Questions
How do I add 90 days to a date?
The calculator adds 90 calendar days to the date you enter. Adding months uses actual calendar months, clamping the day if needed — January 31 plus one month is February 28 (or 29 in a leap year).
What date is 6 months from today?
Enter today's date with 6 months added. The result is the same day in the month six months later, adjusted for shorter months.
Does the calculator handle leap years?
Yes. February 29 exists in leap years, and adding a year to Feb 29 clamps to Feb 28 in non-leap years.
Why does adding a month not equal adding 30 days?
Calendar months have 28 to 31 days, so adding a month keeps the same day number. Adding 30 days instead lands on a different date — choose the unit that matches the calendar you need.