How to add or subtract time from a date
- Enter a start date.
- Choose Add or Subtract.
- Enter an amount and pick the unit: days, weeks, months, or years.
- Read the resulting calendar date. Copy link to share start date, direction, amount, and unit.
Example: 90 days before a deadline
Your project due date is June 1. Choose Subtract, 90, Days, starting from June 1—the result is the calendar day that is ninety days earlier. Use the same flow to find “invoice date plus 30 days” or “warranty end plus one year.”
Days and weeks vs. months and years
Days and weeks shift by a fixed number of calendar days (7 days per week). Months and years respect month length: adding one month to Jan 31 does not jump to Mar 31; it lands on the last day of February. That matches how many contracts and payroll systems interpret “plus one month.”
If you need “how many days between two known dates” instead of a new date, use the date difference calculator. If you only need a countdown to one target day, try the days until calculator.
Common uses
- Payment terms (Net 30, Net 60) from an invoice or ship date
- Return windows, trial periods, and warranty expiry
- Planning backward from a launch or exam date
- Pregnancy or medical “weeks from LMP” style offsets when you already have a start date
For age in years from a birth date, use the age calculator. Browse all tools on date & time calculators.
Frequently asked questions
What date is 30 days from today?
Set start date to today, Add, amount 30, unit Days. The new date shows in the results panel as you type.
How do I subtract 90 days from a date?
Pick the start date, Subtract, 90, Days. Use the sample (Jun 1 minus 90 days) for a deadline-style check.
What's the difference between adding 1 month and adding 30 days?
30 days always moves exactly thirty calendar days. 1 month follows month length—Jan 31 plus one month is not the same as Jan 31 plus 30 days.
What is January 31 plus one month?
Usually the last day of February (28 or 29), not March 31. Choose unit Months on this page to calculate it.
How do I add one year to a date?
Start date → Add → 1 → Years. Leap-day starts use the same calendar-year rules.
When is payment due on Net 60 terms?
From invoice or ship date: Add, 60, Days. If the contract says business days only, use the business days calculator instead.
I already know two dates—how many days between them?
Use the date difference calculator. This page answers “what date is X days after (or before) Y?”
Can the start date be something other than today?
Yes—any calendar start date. Today is only convenient for “30 days from now.”
Can I share my calculation?
Copy link in the results panel saves start date, direction, amount, and unit in the URL.