Date Calculator
Add or subtract a duration from any date to find what date it lands on. Works for days, weeks, months, and years — or any combination.
Quick presets from today
Common Date Calculations
90 days from today — used for prescription refills, visa rules, warranty periods, and legal response windows. Enter today's date, add 90 days.
6 months from a date — common for contract notice periods, probation review dates, and subscription renewals. Adding months accounts for varying month lengths; adding 180 days does not.
1 year from today — useful for annual renewal dates, subscription expiry, and anniversary calculations.
30/60/90 days ago — looking back to find the start of a billing period, when something was filed, or what date a window opened.
Adding Months vs. Adding Days
Adding months and adding days are different operations and give different results:
- Adding 1 month to January 31 gives February 28 (or 29 in a leap year) — the last day of February, because February has no 31st day.
- Adding 31 days to January 31 gives March 3 — 31 exact calendar days later.
For calendar-based calculations (contract terms, subscription periods, anniversary dates), adding months is usually the correct operation. For exact duration calculations (deadlines measured in a specific number of days), adding days is correct.
Frequently Asked Questions
What date is 90 days from today?
Enter today's date, set the addition to 90 days, and read the result. It changes every day as "today" advances, so use the "Use today" button to always start from the current date.
What date was 6 months ago?
Enter today's date, select Subtract, enter 6 months, and read the result.
Why does adding 1 month to January 31 give February 28?
February has 28 days (29 in a leap year). When you add one month and the resulting month doesn't have enough days, the result is clamped to the last day of that month. This is standard behaviour for calendar arithmetic.
What is "30 days net" in contracts?
"Net 30" means payment is due 30 calendar days after the invoice date. Enter the invoice date, add 30 days, and the result is the due date.
