- Home
- Date & Time
- Date Calculator: Add or Subtract Days
Date Calculator: Add or Subtract Days
Start from any date and move forward or back by any mix of years, months, weeks and days. Useful for due dates, notice periods, warranty and return windows, and “net 30” invoices.
- Day of the week
- Saturday
- Total days moved
- 90
- ISO week number
- 1
Saved setups
Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.
Your recent calculations
Results you calculate here are kept on this device so you can come back to them.
Formula
How to use it
- Choose the starting date.
- Choose whether to add or subtract.
- Enter the amounts; leave the units you do not need at 0.
- Read the resulting date and its weekday.
Worked examples
90 days after October 11, 2026
- Resulting date
- Sat, Jan 9, 2027
- Day of the week
- Saturday
One month after January 31, 2026
- Resulting date
- Sat, Feb 28, 2026
- Total days moved
- 28
What “one month later” means
Adding a month moves to the same day number in the next month. When that day does not exist, the result is the last day of the month: January 31 plus one month is February 28 (or 29 in a leap year). Years and months are applied first, then weeks and days.
Common spans
30 days is not the same as one month, and 90 days is not three months: 90 days from October 11 is January 9, while three months is January 11. Legal and financial deadlines say which they mean — read the wording.
Questions people ask
What date is 90 days from today?
Leave the start date as today, choose Add and enter 90 days. From October 11, 2026 the answer is Saturday, January 9, 2027.
Does it skip weekends?
No, it counts calendar days. To count only working days, use the days-from-today calculator set to business days.