Date Add/Subtract Calculator

How to use this tool

Select a start date. Choose the date you want to add to or subtract from. Optionally enter a start time for hour/minute calculations.
Choose operation and amount. Select "Add" or "Subtract" and enter any combination of years, months, weeks, days, hours, and minutes, or choose a common offset preset.
View the result. See the resulting date, day of the week, and how far it is from today.

Common date calculations

Question	How to calculate
What date is 30 days from today?	Start = today, Add 30 Days
What was 90 days ago?	Start = today, Subtract 90 Days
What date is 6 months from now?	Start = today, Add 6 Months
What is the date in 1 year?	Start = today, Add 1 Year
What was the date 2 weeks ago?	Start = today, Subtract 2 Weeks

How month arithmetic works

When adding months, if the resulting month has fewer days than the start date's day, the result is clamped to the last day of that month. For example:

January 31 + 1 month = February 28 (or 29 in a leap year)
March 31 + 1 month = April 30
January 31 + 3 months = April 30

Concrete examples

Project deadlines: "Proposal due 90 days from today" -> enter today's date + 90 days.
Subscription renewal: "Annual subscription started Jan 15, 2024" -> add 1 year -> result: Jan 15, 2025.
Event planning: "Conference is June 10, 2024; need to book venue 6 months prior" -> June 10 − 6 months = Dec 10, 2023.
Legal/contract dates: "30-day notice period starts March 1" -> March 1 + 30 days = March 31.

Month-end edge cases

Adding months can produce unexpected results when the target month has fewer days than the source date:

Jan 31 + 1 month = Feb 28 (or Feb 29 in leap years), not "Feb 31" (invalid).
Aug 31 + 6 months = Feb 28/29, then continuing +1 month = Mar 28/29.
Why? Most date libraries cap the day to the last valid day of the target month. Some libraries (e.g., Moment.js's add()) overflow to the next month instead.

Tip: For contracts or recurring events, specify "last day of month" or "first day of next month" to avoid ambiguity.

Business days vs. calendar days

This calculator counts calendar days, including weekends and holidays. For business-day counts and holiday calendars, use Toolcroft’s Working Days Calculator .

Frequently asked questions

How do I add days to a date?

Select your starting date, choose "Add," enter the number of days, and select "Days" as the unit. The resulting date appears instantly, along with the day of the week and how many days from today it falls.

What date is 90 days from today?

Click Today, then choose the +90 days preset to find the date 90 calendar days from today.

How does adding months handle shorter months?

When you add a month and the resulting month is shorter than the starting month, the day is clamped to the last day of that month. For example, adding 1 month to January 31 gives February 28 (or 29 in a leap year).

Can I add time (hours or minutes)?

Yes. Enter an optional start time and combine hours and minutes with calendar offsets. The result shows the time and accounts for day rollovers.

Can I combine years, months, weeks, and days?

Yes. Enter any combination of years, months, weeks, days, hours, and minutes. Calendar offsets are applied from larger units to smaller units, with month-end dates clamped to the last valid day.