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?

Use this tool with today as the start date, "Add" operation, 90 as the amount, and "Days" as the unit to find the exact date 90 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 - optionally enter a start time in HH:MM format. When adding hours or minutes, the resulting time is shown and day rollovers are handled correctly.

Add or Subtract Days from a Date

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 tool calculates calendar days (including weekends and holidays). For business-day calculations (excluding weekends and optionally holidays):

JavaScript libraries: date-fns addBusinessDays(), Moment Business Days plugin.
Manual formula: For every 5 business days, add 7 calendar days (if no holidays intervene). Example: 10 business days ≈ 14 calendar days.
US Federal holidays: 11 per year (New Year's Day, MLK Day, Presidents' Day, Memorial Day, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving, Christmas). Add extra days if the end date crosses a holiday.